This plant disease lesson on Rhizoctonia diseases of turfgrass (caused by the fungi Rhizoctonia species) includes information on symptoms and signs, pathogen biology, disease cycle and epidemiology, disease management, and the significance of the disease. Selected references are listed and a glossary is also available for use with this resource.

The aim of three years field investigations was to evaluate the effect of bio-preparations Polyversum (B.A.S. Pythium oligandrum ) and Biochikol 020 PC (B. A. S. chitosan) applied on infected tubers by Rhizoctonia solani sclerots during vegetation period. As a standard fungicide Vitavax 2000 FS (B.A.S. karboxin and thiuram) was used. The effect of the mentioned preparations applied at three

Upon screening several fungicides, a few Fusarium oxysporum isolates and one Rhizoctonia solani isolate showed a distinct\\u000a and sudden decrease in sensitivity to TCMTB (2-(thiocyanomethylthio)-benzothiazole). The screening was carried out in Petri\\u000a dishes using an agar medium, mixed with the test fungicides, in the center of which a mycelial piece of the test fungus was\\u000a placed. In several TCMTB-containing plates,

THE EVALUATION OF HIGH TANNIN COTTON LINES FOR RESISTANCE TO RHIZOCTONIA SOLANI AND PYTHIUM APHANIDERMATUM A Thesis by RAYMOND MATTHEW KENNETT Submitted to the Office of Graduate Studies of Texas A&M University in partial... fulfillment of the requirements for the degree of MASTER OF SCIENCE December 2009 Major Subject: Plant Breeding THE EVALUATION OF HIGH TANNIN COTTON LINES FOR RESISTANCE TO RHIZOCTONIA SOLANI AND PYTHIUM APHANIDERMATUM A...

Two tillage practices, chisel plowing (30 cm) and deep moldboard plowing (22 cm), and five rotation crops (oats, lupine, buckwheat,\\u000a broccoli and peas) were studied for their effects on the soil population ofRhizoctonia solani AG-3 and on Rhizoctonia disease on potato. All rotation crops were harvested except buckwheat, which was treated as a green\\u000a manure crop. Chisel plowing significantly reduced

Rhizoctonia solani (Teleomorph: Thanatephorus cucumeris, T. praticola) is a basidiomycetous fungus and a major cause of root diseases of economically important plants. Various isolates of this fungus are also beneficially associated with orchids, may serve as biocontrol agents or remain as saprophytes with roles in decaying and recycling of soil organic matter. R. solani displays several hyphal anastomosis groups (AG) with distinct host and pathogenic specializations. Even though there are reports on the physiological and histological basis of Rhizoctonia-host interactions, very little is known about the molecular biology and control of gene expression early during infection by this pathogen. Proteamic technologies are powerful tools for examining alterations in protein profiles. To aid studies on its biology and host pathogen interactions, a two-dimensional (2-D) gel-based global proteomic study has been initiated. To develop an optimized protein extraction protocol for R. solani, we compared two previously reported protein extraction protocols for 2-D gel analysis of R. solani (AG-4) isolate Rs23. Both TCA-acetone precipitation and phosphate solubilization before TCA-acetone precipitation worked well for R. solani protein extraction, although selective enrichment of some proteins was noted with either method. About 450 spots could be detected with the densitiometric tracing of Coomassie blue-stained 2-D PAGE gels covering pH 4-7 and 6.5-205 kDa. Selected protein spots were subjected to mass spectrometric analysis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Eleven protein spots were positively identified based on peptide mass fingerprinting match with fungal proteins in public databases with the Mascot search engine. These results testify to the suitability of the two optimized protein extraction protocols for 2-D proteomic studies of R. solani. PMID:19202841

Rhizoctonia disease, caused by Rhizoctonia solani is one of the most important fungal diseases in bean fields in Isfahan, Iran. Bean plants showing stem and root cankers were\\u000a collected and Rhizoctonia-like fungi obtained from the samples were identified by anastomosis. Pure cultures of bean isolates of R. solani were identified as AG-4. There were also AG-4 isolates from tomato, potato,

Background The soil borne fungus Rhizoctonia is one of the most important plant pathogenic fungi, with a wide host range and worldwide distribution. In cauliflower (Brassica oleracea var. botrytis), several anastomosis groups (AGs) including both multinucleate R. solani and binucleate Rhizoctonia species have been identified showing different levels of aggressiveness. The infection and colonization process of Rhizoctonia during pathogenic interactions is well described. In contrast, insights into processes during interactions with weak aggressive or non-pathogenic isolates are limited. In this study the interaction of cauliflower with seven R. solani AGs and one binucleate Rhizoctonia AG differing in aggressiveness, was compared. Using microscopic and histopathological techniques, the early steps of the infection process, the colonization process and several host responses were studied. Results For aggressive Rhizoctonia AGs (R. solani AG 1-1B, AG 1-1C, AG 2-1, AG 2-2 IIIb and AG 4 HGII), a higher developmental rate was detected for several steps of the infection process, including directed growth along anticlinal cell walls and formation of T-shaped branches, infection cushion formation and stomatal penetration. Weak or non-aggressive AGs (R. solani AG 5, AG 3 and binucleate Rhizoctonia AG K) required more time, notwithstanding all AGs were able to penetrate cauliflower hypocotyls. Histopathological observations indicated that Rhizoctonia AGs provoked differential host responses and pectin degradation. We demonstrated the pronounced deposition of phenolic compounds and callose against weak and non-aggressive AGs which resulted in a delay or complete block of the host colonization. Degradation of pectic compounds was observed for all pathogenic AGs, except for AG 2-2 IIIb. Ranking the AGs based on infection rate, level of induced host responses and pectin degradation revealed a strong correlation with the disease severity caused by the AGs. Conclusion The differences in aggressiveness towards cauliflower observed among Rhizoctonia AGs correlated with the infection rate, induction of host defence responses and pectin breakdown. All Rhizoctonia AGs studied penetrated the plant tissue, indicating all constitutive barriers of cauliflower were defeated and differences in aggressiveness were caused by inducible defence responses, including cell wall fortifications with phenolic compounds and callose. PMID:19622152

The association of Rhizoctonia spp. with insect-damaged and diseased tissue of the invasive perennial Lepidium draba was documented throughout the range of L. draba that was surveyed in Europe, including Hungary, Austria, Switzerland and France. Samples that could be both maintained under cooled conditions after collection and promptly processed consistently yielded Rhizoctonia solani, 11 isolates of which anastomosed with AG-4,

2-Allylphenol is a biomimetic synthetic fungicide that mimics the compound ginkgol found in gingko fruit (Gingko biloba L.). This systemic fungicide can effectively suppress a wide range of plant diseases, including wheat sharp eyespot (Rhizoctonia cerealis). However, its degradation in environment after application is still unknown. To understand this fungicide degradation, major metabolites of 2-allylphenol in R. cerealis were examined. The parent and metabolites of 2-allylphenol were detected and quantified in the mycelia and liquid medium. Results showed that 2-allylphenol was metabolized and bio-transformed by R. cerealis, and four metabolites were found, including 2-(2-hydroxyphenyl) acetic acid (M1), 2-(2, 3-dihydroxypropyl) phenol (M2), 2-(2-hydroxypropyl)-phenol (M3) and 2-(3-hydroxypropyl)-phenol (M4). Based on the results, we propose that the biodegradation pathway is that 2-allylphenol is rapidly oxidized into metabolite M2 and hydrolyzed into M3 and M4, which formed M2, and carboxylation of M2 to 2-hydroxy-3-(2?-hydroxyphenyl) propionic acid which undergo hydrolyzation and decarboxylation to form M1. 2-Allylphenol can be bio-transformed to new compounds by R. cerealis, suggesting the existence of microbe metabolic pathways for 2-allylphenol. PMID:24530843

The ability of a polyphenoloxidase, the laccase of the fungus Rhizoctonia praticola, to detoxify phenolic pollutants was examined. The growth of the fungus could be inhibited by phenolic compounds, and the effective concentration was dependent on the substituents of the phenol. A toxic amount of a phenolic compound was added to a fungal growth medium in the presence or absence of a naturally occurring phenol, and half of the replicates also received laccase. The medium was then inoculated with R. praticola, and the levels of phenols in the medium were monitored by high-performance liquid chromatography analysis. The addition of the laccase reversed the inhibitory effect of 2,6-xylenol, 4-chloro-2-methylphenol, and p-cresol. Other compounds, e.g., o-cresol and 2,4-dichlorophenol, were detoxified only when laccase was used in conjunction with a natural phenol such as syringic acid. The toxicity of p-chlorophenol and 2,4,5-trichlorophenol could not be overcome by any additions. The ability of the laccase to alter the toxicity of the phenols appeared to be related to the capacity of the enzyme to decrease the levels of the parent compound by transformation or cross-coupling with another phenol.

Validamycin A decreased the biomass and extracellular protein produced by cultures of Rhizoctonia solani A79 grown on medium containing cellulose as the carbon source. In the presence of the antibiotic, the production of inducible enzymes active on filter paper (FPase), carboxymethylcellulose (CMCase) and (cellobiase) was decreased, but not the production of constitutive enzymes involved in hemicellulose (xylanase) and pectin (polygalacturonase)

The subterranean parts of 1585 wild plants (weeds) belonging to 52 species, found in potato fields in the northern part of the Netherlands were examined for the presence ofRhizoctonia solani. The fungus could be isolated from 30 plants belonging to 12 species. Of these isolates 62% proved to be pathogenic to potato sprouts.

ABSTRACT The ability to identify diseases early and quantify severity accurately is crucial in plant disease assessment and management. This study was conducted to assess changes in the spectral reflectance of sunlight from plots of creeping bentgrass during infection by Rhizoctonia solani, the cause of Rhizoctonia blight, and to evaluate multispectral radiometry as a tool to quantify Rhizoctonia blight severity. After inoculation of 6-year-old creeping bentgrass turf with R. solani anastomosis group 2-2, reflectance of sunlight from the foliar canopy was measured at light wavelengths of 460 nm (blue) to 810 nm (near infrared [NIR]), at 50-nm intervals. Visual estimates of disease severity and percentage of canopy reflectance were made daily throughout each of three epidemics of Rhizoctonia blight from the onset of visible symptoms until maximum disease severity was reached. In each experiment, linear regression analysis revealed a significant reduction in the percentage of NIR (760 and 810 nm) reflectance as disease severity increased. However, in the majority of analyses, regression models explained <50% of the variability between components. Multispectrum radiometry appears to function best when used to assess differences in disease severity at discrete points in time rather than over an entire epidemic. PMID:18944925

In Tocantins State, Northern Brazil, the incidence of Rhizoctonia sheath blight on rice is important, causing significant yield losses on rice crops under irrigation. The main objective of this research was to determine the anastomosis group (AG) of R. solani associated with rice in that area, testing the hypothesis that these isolates are from the AG- 1 IA, which is

Rhizoctonia blight is a common and serious disease of many turfgrass species. The most widespread causal agent, Thanatephorus cucumeris (anamorph: R. solani), consists of several genetically different subpopulations. In addition, Waitea circinata varieties zeae, oryzae and circinata (anamorph: Rhizoctonia spp.) also can cause the disease. Accurate identification of the causal pathogen is important for effective management of the disease. It is challenging to distinguish the specific causal pathogen based on disease symptoms or macroscopic and microscopic morphology. Traditional methods such as anastomosis reactions with tester isolates are time consuming and sometimes difficult to interpret. In the present study universally primed PCR (UP-PCR) fingerprinting was used to assess genetic diversity of Rhizoctonia spp. infecting turfgrasses. Eighty-four Rhizoctonia isolates were sampled from diseased turfgrass leaves from seven distinct geographic areas in Virginia and Maryland. Rhizoctonia isolates were characterized by ribosomal DNA internal transcribed spacer (rDNA-ITS) region and UP-PCR. The isolates formed seven clusters based on ITS sequences analysis and unweighted pair group method with arithmetic mean (UPGMA) clustering of UP-PCR markers, which corresponded well with anastomosis groups (AGs) of the isolates. Isolates of R. solani AG 1-IB (n = 18), AG 2-2IIIB (n = 30) and AG 5 (n = 1) clustered separately. Waitea circinata var. zeae (n = 9) and var. circinata (n = 4) grouped separately. A cluster of six isolates of Waitea (UWC) did not fall into any known Waitea variety. The binucleate Rhizoctonia-like fungi (BNR) (n = 16) clustered into two groups. Rhizoctonia solani AG 2-2IIIB was the most dominant pathogen in this study, followed by AG 1-IB. There was no relationship between the geographic origin of the isolates and clustering of isolates based on the genetic associations. To our knowledge this is the first time UP-PCR was used to characterize Rhizoctonia, Waitea and Ceratobasidium isolates to their infra-species level. PMID:23709576

A new benzophenone, named rhizoctonic acid (1), together with three known compounds monomethylsulochrin (2), ergosterol (3) and 3?,5?,6?-trihydroxyergosta-7,22-diene (4) were isolated through bioassay-guided fractionations from the culture of Rhizoctonia sp. (Cy064), an endophytic fungus in the leaf of Cynodon dactylon. The structure of the new acid 1 was elucidated to be 5-hydroxy-2-(2-hydroxy-6-methoxy-4-methylbenzoyl)-3-methoxybenzoic acid by a combination of spectral analyses. Furthermore,

Summary \\u000a Trichoderma harzianum preparations was used in two successive field experiments in commercial strawberry nurseries and fruiting fields. Disease\\u000a severity ofRhizoctonia solani in daughter plants was reduced by 18–46 % in the treated nursery plots. Infestation of nursery soil with the pathogen, as\\u000a tested by planting beans in soil samples was reduced by the Trichoderma treatment by up to 92%

RFLP analyses of a portion of the 28S rDNA gene region were conducted by using four restriction endonucleases for 57 isolates\\u000a of 13 intraspecific groups (ISGs) representing 7 anastomosis groups (AGs) ofRhizoctonia solani. Variations in the PCR-amplified rDNA products and the polymorphisms on digestion with restriction enzymes (BamHI,HaeIII,HhaI andHpaII) were observed among three AGs, AG 1, 2 and 4. These

This research demonstrates the role of antimicrobial volatiles produced by Muscodor albus in disease control in soil and potting mix. The volatiles controlled damping-off of broccoli seedlings when pots containing\\u000a soil or soilless potting mix infested with Rhizoctonia solani were placed in the presence of active M. albus culture without physical contact in closed containers. Conversely, plugs of R. solani

In this study, the effects of medicinal plant extracts on the development of mycelium in the following phytopathogenic fungi\\u000a were evaluated: Phytophthora capsici, Rhizoctonia solani, Fusarium solani, Colletotrichum gloeosprorioides, and Botrytis cinera. Of the 26 medicinal plants tested, six plant extracts showed antifungal activity against phytopathogenic fungi. The highest\\u000a antifungal activity was exerted against R. solani by the n-hexane fraction

Rhizoctonia solani AG-2-2 was isolated from wilting and dying plants of sulla (Hedysarum coronarium), which is currently being assessed in eastern and southern Australia for its potential as a pasture and forage legume. Infected\\u000a plants in the field had extensive rotting of the taproot, lateral roots and crown. Koch’s postulates were fulfilled using\\u000a three inoculation methods. The disease may pose

Ninety seven Rhizoctonia isolates were collected from different Brassica species with typical Rhizoctonia symptoms in different provinces of Vietnam. The isolates were identified using staining of nuclei and sequencing of the rDNA-ITS barcoding gene. The majority of the isolates were multinucleate R. solani and four isolates were binucleate Rhizoctonia belonging to anastomosis groups (AGs) AG-A and a new subgroup of A-F that we introduce here as AG-Fc on the basis of differences in rDNA-ITS sequence. The most prevalent multinucleate AG was AG 1-IA (45.4% of isolates), followed by AG 1-ID (17.5%), AG 1-IB (13.4%), AG 4-HGI (12.4%), AG 2-2 (5.2%), AG 7 (1.0%) and an unknown AG related to AG 1-IA and AG 1-IE that we introduce here as AG 1-IG (1.0%) on the basis of differences in rDNA-ITS sequence. AG 1-IA and AG 1-ID have not been reported before on Brassica spp. Pathogenicity tests revealed that isolates from all AGs, except AG-A, induced symptoms on detached leaves of several cabbage species. In in vitro tests on white cabbage and Chinese cabbage, both hosts were severely infected by AG 1-IB, AG 2-2, AG 4-HGI, AG 1-IG and AG-Fc isolates, while under greenhouse conditions, only AG 4-HGI, AG 2-2 and AG-Fc isolates could cause severe disease symptoms. The occurrence of the different AGs seems to be correlated with the cropping systems and cultural practices in different sampling areas suggesting that agricultural practices determine the AGs associated with Brassica plants in Vietnam. PMID:25372406

A split-root technique was used to examine the interaction between Pratylenchus penetrans and the cortical root-rotting pathogen Rhizoctonia fragariae in strawberry black root rot. Plants inoculated with both pathogens on the same half of a split-root crown had greater levels of root rot than plants inoculated separately or with either pathogen alone. Isolation of R. fragariae from field-grown roots differed with root type and time of sampling. Fungal infection of structural roots was low until fruiting, whereas perennial root colonization was high. Isolation of R. fragariae from feeder roots was variable, but was greater from feeder roots on perennial than from structural roots. Isolation of the fungus was greater from structural roots with nematode lesions than from non-symptomatic roots. Rhizoctonia fragariae was a common resident on the sloughed cortex of healthy perennial roots. From this source, the fungus may infect additional roots. The direct effects of lesion nematode feeding and movement are cortical cell damage and death. Indirect effects include discoloration of the endodermis and early polyderm formation. Perhaps weakened or dying cells caused directly or indirectly by P. penetrans are more susceptible to R. fragariae, leading to increased disease. PMID:19265969

An antibiotic-producing and hydrogen-cyanide-producing rhizobacteria strain Bacillus BS2 showed a wide range of antifungal activity against many Fusarium sp. and brinjal wilt disease pathogen Rhizoctonia solani. Seed bacterization with the strain BS2 promoted seed germination and plant growth in leguminous plants Phaseolus vulgaris and non-leguminous plants Solanum melongena L, Brassica oleracea var. capitata, B. oleraceae var. gongylodes and Lycopersicon esculentum Mill in terms of relative growth rate, shoot height, root length, total biomass production and total chlorophyll content of leaves. Yield of bacterized plants were increased by 10 to 49% compared to uninoculated control plants. Brinjal sapling raised through seed bacterization by the strain BS2 showed a significantly reduced wilt syndrome of brinjal caused by Rhizoctonia solani. Control of wilt disease by the bacterium was clue to the production of antibiotic-like substances, whereas plant growth-promotion was due to the activity of hydrogen cyanide. Root colonization study confirmed that the introduced bacteria colonized the roots and occupied 23-25% of total aerobic bacteria, which was confirmed using dual antibiotic (nalidixic acid and streptomycin sulphate) resistant mutant strain. The results obtained through this investigation suggested the potentiality of the strain BS2 to be used as a plant growth promoter and suppressor of wilt pathogen. PMID:15266911

Mycorrhizal association is known to be important to orchid species, and a complete understanding of the fungi that form mycorrhizas is required for orchid ecology and conservation. Liparis japonica (Orchidaceae) is a widespread terrestrial photosynthetic orchid in Northeast China. Previously, we found the genetic diversity of this species has been reduced recent years due to habitat destruction and fragmentation, but little was known about the relationship between this orchid species and the mycorrhizal fungi. The Rhizoctonia-like fungi are the commonly accepted mycorrhizal fungi associated with orchids. In this study, the distribution, diversity and specificity of culturable Rhizoctonia-like fungi associated with L. japonica species were investigated from seven populations in Northeast China. Among the 201 endophytic fungal isolates obtained, 86 Rhizoctonia-like fungi were identified based on morphological characters and molecular methods, and the ITS sequences and phylogenetic analysis revealed that all these Rhizoctonia-like fungi fell in the same main clade and were closely related to those of Tulasnella calospora species group. These findings indicated the high mycorrhizal specificity existed in L. japonica species regardless of habitats at least in Northeast China. Our results also supported the wide distribution of this fungal partner, and implied that the decline of L. japonica in Northeast China did not result from high mycorrhizal specificity. Using culture-dependent technology, these mycorrhizal fungal isolates might be important sources for the further utilizing in orchids conservation. PMID:25140872

The soil fungus Rhizoctonia solani is a pathogen of agricultural crops. Here, we report on the 51,705,945 bp draft consensus genome sequence of R. solani strain Rhs1AP. A comprehensive understanding of the heterokaryotic genome complexity and organization of R. solani may provide insight into the plant disease ecology and adaptive behavior of the fungus. PMID:25359908

The soil fungus Rhizoctonia solani is a pathogen of agricultural crops. Here, we report on the 51,705,945 bp draft consensus genome sequence of R. solani strain Rhs1AP. A comprehensive understanding of the heterokaryotic genome complexity and organization of R. solani may provide insight into the plant disease ecology and adaptive behavior of the fungus. PMID:25359908

Mycorrhizal association is known to be important to orchid species, and a complete understanding of the fungi that form mycorrhizas is required for orchid ecology and conservation. Liparis japonica (Orchidaceae) is a widespread terrestrial photosynthetic orchid in Northeast China. Previously, we found the genetic diversity of this species has been reduced recent years due to habitat destruction and fragmentation, but little was known about the relationship between this orchid species and the mycorrhizal fungi. The Rhizoctonia-like fungi are the commonly accepted mycorrhizal fungi associated with orchids. In this study, the distribution, diversity and specificity of culturable Rhizoctonia-like fungi associated with L. japonica species were investigated from seven populations in Northeast China. Among the 201 endophytic fungal isolates obtained, 86 Rhizoctonia-like fungi were identified based on morphological characters and molecular methods, and the ITS sequences and phylogenetic analysis revealed that all these Rhizoctonia-like fungi fell in the same main clade and were closely related to those of Tulasnella calospora species group. These findings indicated the high mycorrhizal specificity existed in L. japonica species regardless of habitats at least in Northeast China. Our results also supported the wide distribution of this fungal partner, and implied that the decline of L. japonica in Northeast China did not result from high mycorrhizal specificity. Using culture-dependent technology, these mycorrhizal fungal isolates might be important sources for the further utilizing in orchids conservation. PMID:25140872

Rhizoctonia bare patch and root rot disease of wheat, caused by Rhizoctonia solani AG-8, develops as distinct patches of stunted plants and limits the yield of direct-seeded (no-till) wheat in the Pacific Northwest of the United States. At the site of a long-term cropping systems study near Ritzville, WA, a decline in Rhizoctonia patch disease was observed over an 11-year period. Bacterial communities from bulk and rhizosphere soil of plants from inside the patches, outside the patches, and recovered patches were analyzed by using pyrosequencing with primers designed for 16S rRNA. Taxa in the class Acidobacteria and the genus Gemmatimonas were found at higher frequencies in the rhizosphere of healthy plants outside the patches than in that of diseased plants from inside the patches. Dyella and Acidobacteria subgroup Gp7 were found at higher frequencies in recovered patches. Chitinophaga, Pedobacter, Oxalobacteriaceae (Duganella and Massilia), and Chyseobacterium were found at higher frequencies in the rhizosphere of diseased plants from inside the patches. For selected taxa, trends were validated by quantitative PCR (qPCR), and observed shifts of frequencies in the rhizosphere over time were duplicated in cycling experiments in the greenhouse that involved successive plantings of wheat in Rhizoctonia-inoculated soil. Chryseobacterium soldanellicola was isolated from the rhizosphere inside the patches and exhibited significant antagonism against R. solani AG-8 in vitro and in greenhouse tests. In conclusion, we identified novel bacterial taxa that respond to conditions affecting bare patch disease symptoms and that may be involved in suppression of Rhizoctonia root rot and bare batch disease. PMID:24056471

Rhizoctonia bare patch and root rot disease of wheat, caused by Rhizoctonia solani AG-8, develops as distinct patches of stunted plants and limits the yield of direct-seeded (no-till) wheat in the Pacific Northwest of the United States. At the site of a long-term cropping systems study near Ritzville, WA, a decline in Rhizoctonia patch disease was observed over an 11-year period. Bacterial communities from bulk and rhizosphere soil of plants from inside the patches, outside the patches, and recovered patches were analyzed by using pyrosequencing with primers designed for 16S rRNA. Taxa in the class Acidobacteria and the genus Gemmatimonas were found at higher frequencies in the rhizosphere of healthy plants outside the patches than in that of diseased plants from inside the patches. Dyella and Acidobacteria subgroup Gp7 were found at higher frequencies in recovered patches. Chitinophaga, Pedobacter, Oxalobacteriaceae (Duganella and Massilia), and Chyseobacterium were found at higher frequencies in the rhizosphere of diseased plants from inside the patches. For selected taxa, trends were validated by quantitative PCR (qPCR), and observed shifts of frequencies in the rhizosphere over time were duplicated in cycling experiments in the greenhouse that involved successive plantings of wheat in Rhizoctonia-inoculated soil. Chryseobacterium soldanellicola was isolated from the rhizosphere inside the patches and exhibited significant antagonism against R. solani AG-8 in vitro and in greenhouse tests. In conclusion, we identified novel bacterial taxa that respond to conditions affecting bare patch disease symptoms and that may be involved in suppression of Rhizoctonia root rot and bare batch disease. PMID:24056471

Effect of benomyl and thiophanate-methyl on various metabolic activities of Rhizoctonia solani was investigated. Both fungitoxicants strongly reduced endogenous whole cell and mitochondrial respiration by inhibiting one or the other key enzymes of electron transport chain; the activity of cytochrome oxidase being most markedly inhibited. Incorporation of 3II-thymidine was reduced by both while there was little or no inhibition in the rate of incorporation of 14C-uracil and 14C-leucine. Cell permeability was not affected to any appreciable extent and there was a little release of cellular components from the treated cells only at prolonged incubation. It is concluded that benomyl and thiophanate-methyl have a similar mode of action which primarily involves inhibition of respiratory activities, and as a consequence the biosynthesis of DNA is reduced. PMID:183584

In this study, the biocontrol abilities of water-soluble and volatile metabolites of three different isolates of Trichoderma (T. asperellum, T. harzianum and Trichoderma spp.) against soil borne plant pathogen Rhizoctonia solani were investigated both in vitro and in vivo. The results showed for the first time that mycelial growth inhibition of the pathogen was 74.4-67.8% with water-soluble metabolites as compared to 15.3-10.6% with volatile metabolites in vitro. In vivo antagonistic activity of Trichoderma isolates against R. solani was evaluated on bean plants under laboratory and greenhouse conditions. We observed that T. asperellum was more effective and consistent, lowering disease incidence up to 19.3% in laboratory and 30.5% in green house conditions. These results showed that three isolates of Trichoderma could be used as effective biocontrol agents against R. solani. PMID:25033669

Rhizoctonia solani is an important necrotrophic fungal pathogen which causes disease on diverse plant species. It has been classified into 14 genetically distinct anastomosis groups (AGs), however, very little is known about their genomic diversity. AG1-IA causes sheath blight disease in rice and controlling this disease remains a challenge for sustainable rice cultivation. Recently the draft genome sequences of AG1-IA (rice isolate) and AG1-IB (lettuce isolate) had become publicly available. In this study, using comparative genomics, we report identification of 3,942 R. solani genes that are uniquely present in AG1-IA. Many of these genes encode important biological, molecular functions and exhibit dynamic expression during in-planta growth of the pathogen in rice. Based upon sequence similarity with genes that are required for plant and human/zoonotic diseases, we identified several putative virulence/pathogenicity determinants amongst AG1-IA specific genes. While studying the expression of 19 randomly selected genes, we identified three genes highly up-regulated during in-planta growth. The detailed in silico characterization of these genes and extent of their up-regulation in different rice genotypes, having variable degree of disease susceptibility, suggests their importance in rice-Rhizoctonia interactions. In summary, the present study reports identification, functional characterization of AG1-IA specific genes and predicts important virulence determinants that might enable the pathogen to grow inside hostile plant environment. Further characterization of these genes would shed useful insights about the pathogenicity mechanism of AG1-IA on rice. PMID:25070039

Israeli farmers export 250,000 tons of potato tubers annually, ?40,000 tons of which are harvested early, before skin set. In recent years, there has been an increase in the occurrence of dark skin spots on early-harvested potato tubers ('Nicola') packed in large bags containing peat to retain moisture. The irregular necrotic spots form during storage and overseas transport. Characterization of the conditions required for symptom development indicated that bag temperature after packing is 11 to 13°C and it reaches the target temperature (8°C) only 25 days postharvest. This slow decrease in temperature may promote the establishment of pathogen infection. Isolates from typical lesions were identified as Rhizoctonia spp., and Koch's postulates were completed with 25 isolates by artificial inoculation performed at 13 to 14°C. Phylogenetic analysis, using the internal transcribed spacer sequences (ITS1 and ITS2) of rDNA genes, assigned three isolates to anastomosis group 3 of Rhizoctonia solani. Inoculation of wounded tubers with mycelium of these R. solani isolates resulted in an oversuberization response in the infected area. With isolate Rh17 of R. solani, expression of the suberin biosynthesis-related genes StKCS6 and CYP86A33 increased 6.8- and 3.4-fold, respectively, 24 h postinoculation, followed by a 2.9-fold increase in POP_A, a gene associated with wound-induced suberization, expression 48 h postinoculation, compared with the noninoculated tubers. We suggest that postharvest dark spot disease is an oversuberization response to R. solani of AG-3 infection that occurs prior to tuber skin set. PMID:21391824

To date, much of the genetics of the basidiomycete Thanatephorus cucumeris (anamorph = Rhizoctonia solani) remains unknown. Here, we present a population genetics study using codominant markers to augment laboratory analyses. Seven single-copy nuclear RFLP markers were used to examine 182 isolates of Rhizoctonia solani AG-1 IA collected from six commercial rice fields in Texas. Thirty-six multilocus RFLP genotypes were identified. Population subdivision analyses indicated a high degree of gene flow/migration between the six geographic populations. Tests for Hardy-Weinberg equilibrium (HWE) among the 36 multilocus RFLP genotypes revealed that four of the seven loci did not significantly differ from HWE. Subsequent analysis demonstrated that departures from HWE at the three remaining loci were due to an excess of heterozygotes. Data presented here suggest that R. solani AG-1 IA is actively outbreeding (heterothallic). Possible explanations for heterozygote excess, which was observed at all seven RFLP loci, are discussed. PMID:10669581

The field symptoms of Eradu patch are distinct, stunted patches in narrow-leaf lupin and ill-thrift patches in barley. The\\u000a pathogen, a thin, binucleate Rhizoctonia (TBR), is difficult to isolate with standard methods. To develop an assay specific to TBR, the ribosomal RNA ITS region was\\u000a amplified and a 610 bp section including the conserved 5.8S region was sequenced. This sequence

Two fungal and three bacterial isolates were tested for efficacy in control of damping-off disease and survival under a range of conditions. In two experiments withCapsicum annuumseedlings in pasteurized potting medium at 25°C, two binucleateRhizoctoniaisolates (BNR1 and BNR2) were more effective againstRhizoctonia solanianastomosis group 4 (AG 4) than the bacteria,Bacillus amyloliquefaciens,and two isolates ofPseudomonas putida.Inin vitrotests, all five biocontrol isolates

Fungi often produce the phenoloxidase enzyme laccase during interactions with other organisms, an obser- vation relevant to the development of biocontrols. By incorporating the laccase substrate 2,2*-azino-bis(3- ethylbenzthiazoline-6-sulfonic acid) (ABTS) into agar, we analyzed laccase induction in the plant-pathogenic fungus Rhizoctonia solani when paired against isolates of the soil bacterium Pseudomonas fluorescens. Substan- tial induction of R. solani laccase was

A 3-year study was conducted to evaluate the effectiveness of two disease-suppressive Streptomyces spp. to control sugar beet Rhizoctonia solani damping off under field conditions. Streptomyces seed treatments reduced seedling damping off in naturally (2005) and artificially (2006 and 2007) infested soils. All biocontrol agents provided better efficacy than Vitavax to control seedling damping-off. There were no significant differences among

Rhizoctonia solani AG-2-2 is the causal agent of Rhizoctonia root and crown rot in sugar beet; however, recent increases in disease incidence and severity were grounds to reevaluate this pathosystem. To assess the capacity at which other anastomosis groups (AGs) are able to infect sugar beet, 15 AGs and intraspecific groups (ISGs) were tested for pathogenicity on resistant ('FC708 CMS') and susceptible ('Monohikari') seedlings and 10-week-old plants. Several AGs and ISGs were pathogenic on seedlings regardless of host resistance but only AG-2-2 IIIB and AG-2-2 IV caused significant disease on 10-week-old plants. Because fungicides need to be applied prior to infection for effective disease control, temperature and moisture parameters were assessed to identify potential thresholds that limit infection. Root and leaf disease indices were used to evaluate disease progression of AG-2-2 IIIB- and AG-2-2 IV-inoculated plants in controlled climate conditions of 7 to 22 growing degree days (GDDs) per day. Root disease ratings were positively correlated with increasing temperature of both ISGs, with maximum disease symptoms occurring at 22 GDDs/day. No disease symptoms were evident from either ISG at 10 GDDs/day but disease symptoms did occur in plants grown in growth chambers set to 11 GDDs/day. Using growth chambers adjusted to 22 GDDs/day, disease was evaluated at 25, 50, 75, and 100% moisture-holding capacity (MHC). Disease symptoms for each ISG were highest in soils with 75 and 100% MHC but disease still occurred at 25% MHC. Isolates were tested for their ability to cause disease at 1, 4, and 8 cm from the plant hypocotyl. Only AG-2-2 IIIB was able to cause disease symptoms at 8 cm during the evaluation period. In all experiments, isolates of AG-2-2 IIIB were found to be more aggressive than AG-2-2 IV. Using environmental parameters that we identified as the most conducive to disease development, azoxystrobin, prothioconazole, pyraclostrobin, difenoconazole/propiconazole, flutolanil, polyoxin D, and a water control were evaluated for their ability to suppress disease development by AG-2-2 IIIB and AG-2-2 IV 17 days after planting. Flutolanil, polyoxin-D, and azoxystrobin provided the highest level of disease suppression. Because R. solani AG-2-2 IIIB and AG-2-2 IV are affected by temperature and moisture, growers may be able to evaluate environmental parameters for optimization of fungicide application. PMID:20528187

ABSTRACT Eight different 3-year cropping systems, consisting of soybean-canola, soybean-barley, sweet corn-canola, sweet corn-soybean, green bean-sweet corn, canola-sweet corn, barley-clover, and continuous potato (non-rotation control) followed by potato as the third crop in all systems, were established in replicated field plots with two rotation entry points in Presque Isle, ME, in 1998. Cropping system effects on soil microbial community characteristics based on culturable soil microbial populations, single carbon source substrate utilization (SU) profiles, and whole-soil fatty acid methyl ester (FAME) profiles were evaluated in association with the development of soilborne diseases of potato in the 2000 and 2001 field seasons. Soil populations of culturable bacteria and overall microbial activity were highest following barley, canola, and sweet corn crops, and lowest following continuous potato. The SU profiles derived from BIOLOG ECO plates indicated higher substrate richness and diversity and greater utilization of certain carbohydrates, carboxylic acids, and amino acids associated with barley, canola, and some sweet corn rotations, indicating distinct differences in functional attributes of microbial communities among cropping systems. Soil FAME profiles also demonstrated distinct differences among cropping systems in their relative composition of fatty acid types and classes, representing structural attributes of microbial communities. Fatty acids most responsible for differentiation among cropping systems included 12:0, 16:1 omega5c, 16:1 omega7c, 18:1 omega9c, and 18:2omega6c. Based on FAME biomarkers, barley rotations resulted in higher fungi-to-bacteria ratios, sweet corn resulted in greater mycorrhizae populations, and continuous potato produced the lowest amounts of these and other biomarker traits. Incidence and severity of stem and stolon canker and black scurf of potato, caused by Rhizoctonia solani, were reduced for most rotations relative to the continuous potato control. Potato crops following canola, barley, or sweet corn provided the lowest levels of Rhizoctonia disease and best tuber quality, whereas potato crops following clover or soybean resulted in disease problems in some years. Both rotation crop and cropping sequence were important in shaping the microbial characteristics, soilborne disease, and tuber qualities. Several microbial parameters, including microbial populations and SU and FAME profile characteristics, were correlated with potato disease or yield measurements in one or both harvest years. In this study, we have demonstrated distinctive effects of specific rotation crops and cropping sequences on microbial communities and have begun to relate the implications of these changes to crop health and productivity. PMID:18944206

Brown patch, incited by Rhizoctonia solani Kuhn, and Pythium blight, caused by Pythium spp. are two of the diseases most frequently observed on turfgrass in high maintenance stands, as on golf courses. In such conditions the control strategies, based on chemicals, are particularly difficult due to the scarcity of fungicides registered for turf in Italy. The results obtained in experimental trials carried out to evaluate the efficacy of chemical and biological products against brown patch and Pythium blight are reported. On mature turfgrass, maintained under fairway conditions, azoxystrobin, and trifoxystrobin, not yet registered on turf, were very effective against brown patch. Tebuconazole, applied in three different formulations, was very effective against R. solani, while Trichoderma spp. and azadiractine did not control the pathogen. In greenhouse conditions on Agrostis stolonifera, in the presence of severe disease incidence, due to artificial inoculation, benalaxyl-M satisfactorily controlled Pythium blight; Trichoderma spp. as well as a commercial formulation of T. harzianum, applied one week before the inoculation, were not effective. Among the fungicides not yet registered for use on turfgrass in Italy, metalaxyl-M + mancozeb was effective against Pythium blight. PMID:15151284

Plant protection through siderophore producing rhizobacteria (SPR) has emerged as a sustainable approach for crop health management. In present study, 220 bacteria isolated from tomato rhizosphere were screened for in vitro antagonistic activity against Rhizoctonia solani AG-4. Nine potent antagonistic strains viz., Alcaligenes sp. (MUN1, MB21, and MPF37), Enterobacter sp. (MPM1), Pseudomonas sp. (M10A and MB65), P. aeruginosa (MPF14 and MB123) and P. fluorescens (MPF47) were identified on the basis of physiological characters and 16S rDNA sequencing. These strains were able to produce hydrolytic enzymes, hydrogen cyanide, indole acetic acid, although, only few strains were able to solubilize phosphate. Two strains (MB123 and MPF47) showed significant disease reduction in glasshouse conditions were further evaluated under field conditions using three different application methods. Application of P. fluorescens (MPF47) in nursery as soil mix?+?seedling root treatments prior to transplantation resulted in significant disease reduction compared to control. Total chlorophyll and available iron were significantly higher in the MPF47 treated plants in contrast to infected control. In conclusion, siderophore producing bacteria MPF47 have strong biocontrol abilities and its application as soil mix?+?seedling root treatments provided strong shield to plant roots against R. solani and could be used for effective bio-management of pathogen. PMID:23686438

A total of 137 bacterial isolates from surface sterilized root, stem, and nodule tissues of soybean were screened for their antifungal activity against major phytopathogens like Rhizoctonia bataticola, Macrophomina phaseolina, Fusarium udam, and Sclerotium rolfsii. Nine bacterial endophytes suppressed the pathogens under in vitro plate assay. These were characterized biochemically and identified at the genus level based on their partial sequence analysis of 16S rDNA. Eight of the isolates belonged to Bacillus and one to Paenibacillus. The phylogenetic relationship among the selected isolates was studied and phylogenetic trees were generated. The selected isolates were screened for biocontrol traits like production of hydrogen cyanide (HCN), siderophore, hydrolytic enzymes, antibiotics, and plant growth promoting traits like indole 3-acetic acid production, phosphate solubilization, and nitrogen fixation. A modified assessment scheme was used to select the most efficient biocontrol isolates Paenibacillus sp. HKA-15 (HKA-15) and Bacillus sp. HKA-121 (HKA-121) as potential candidates for charcoal rot biocontrol as well as soybean plant growth promotion. PMID:19067044

Rice sheath blight, caused by Rhizoctonia solani, is considered a worldwide destructive rice disease and leads to considerable yield losses. A bio-control agent, Paenibacillus kribbensis PS04, was screened to resist against the pathogen. The inhibitory effects were investigated (>80 %) by the growth of the hyphae. Microscopic observation of the hypha structure manifested that the morphology of the pathogenic mycelium was strongly affected by P. kribbensis PS04. To explore essentially inhibitory mechanisms, proteomic approach was adopted to identify differentially expressed proteins from R. solani GD118 in response to P. kribbensis PS04 using two-dimensional gel electrophoresis. Protein profiling was used to identify 13 differential proteins: 10 proteins were found to be down-regulated while 3 proteins were up-regulated. These proteins were involved in material and energy metabolism, antioxidant activity, protein folding and degradation, and cytoskeleton regulation. Among them, material and energy metabolism was differentially regulated by P. kribbensis PS04. Protein expression was separately inhibited by the bio-control agent in oxidation resistance, protein folding and degradation, and cytoskeleton regulation. Proteome changes of the mycelium assist in understanding how the pathogen was directly suppressed by P. kribbensis PS04. PMID:25164959

Microplot and small field-plot experiments were conducted to determine the effects of Pratylenchus penetrans on strawberry yield over several seasons and to evaluate the effects of nematode control on strawberry vigor and yield. Pratylenchus penetrans alone or in combination with the black root rot pathogen, Rhizoctonia fragariae, reduced strawberry yield in microplots over time. There were no differences in effects on yield among R. fragariae anastomosis groups A, G, or I. The interaction of the two pathogens appeared to be additive rather than synergistic. In field plots infested with P. penetrans alone, plant vigor and yield were increased by the application of carbofuran and fenamiphos nematicides. Nematode control was transitory, as P. penetrans populations were initially suppressed but were not different in samples taken 10 months after treatment. These data highlight the error in associating causality between plant damage and nematode populations based on a correlation of root disease with nematode diagnostic assays from severely diseased plants. These findings may help to explain how nematode numbers can sometimes be higher in healthy plants than in severely diseased plants that lack sufficient roots to maintain nematode populations. Because nematode populations from up to a year before harvest are better correlated with berry yield, preplant nematode diagnostic assays taken a year in advance of harvest may be superior in predicting damage to perennial strawberry yield. PMID:19270914

Two field isolates of Rhizoctonia solani were isolated from infected paddy plants in Malaysia. These isolates were verified via ITS-rDNA analysis that yielded ~720?bp products of the ITS1-5.8S-ITS4 region, respectively. The sequenced products showed insertion and substitution incidences which may result in strain diversity and possible variation in disease severity. These strains showed some regional and host-specific relatedness via Maximum Likelihood and further phylogenetic analysis via Maximum Parsimony showed that these strains were closely related to R. solani AG1-1A (with 99-100% identity). Subsequent to strain verification and analysis, these isolates were used in the screening of twenty rice varieties for tolerance or resistance to sheath blight via mycelial plug method where both isolates (1801 and 1802) showed resistance or moderate resistance to Teqing, TETEP, and Jasmine 85. Isolate 1802 was more virulent based on the disease severity index values. This study also showed that the mycelial plug techniques were efficient in providing uniform inoculum and humidity for screening. In addition this study shows that the disease severity index is a better mode of scoring for resistance compared to lesion length. These findings will provide a solid basis for our future breeding and screening activities at the institution. PMID:25258710

Rhizoctonia solani, teleomorph Thanatephorus cucumeris, is a polyphagous necrotrophic plant pathogen of the Basidiomycete order that is split into 14 different anastomosis groups (AGs) based on hyphal interactions and host range. In this investigation, quantitative real-time PCR (qRT-PCR) techniques were used to determine potential pathogenicity factors of R. solani in the AG1-IA/rice and AG3/potato pathosystems. These factors were identified by mining for sequences of pathogen origin in a library of rice tissue infected with R. solani AG1-IA and comparing these sequences against the recently released R. solani AG3 genome. Ten genes common to both AGs and two specific to AG1-IA were selected for expression analysis by qRT-PCR. Results indicate that a number of genes are similarly expressed by AG1 and AG3 during the early stages of pathogenesis. Grouping of these pathogenicity factors based on relatedness of expression profiles suggests three key events are involved in R. solani pathogenesis: early host contact and infiltration, adjustment to the host environment, and pathogen proliferation through necrotic tissue. Further studies of the pathogenesis-associated genes identified in this project will enable more precise elucidation of the molecular mechanisms that allow for the widespread success of R. solani as a phytopathogen and allow for more targeted, effective methods of management. PMID:21909999

For clarification of the antagonistic mechanism of Bacillus pumilus SQR-N43 (N43) against Rhizoctonia solani Q1, production of antibiotics by N43 was determined, and the effect of the antibiotics on the pathogen mycelium was microscopically observed. Further more, the control efficiencies of the antifungal compounds on damping-off disease were investigated. The results obtained are listed as follows: N43 produced antibiotic substances towards R. solani Q1 at logarithmic growth phase. The antibiotics caused hyphal deformation and enlargement of cytoplasmic vacuoles in R. solani Q1 mycelia. 70% saturation of ammonium sulfate made a complete precipitation of the antibiotics in culture broth. When treated with protease K and trypsase, the activities of antibiotics were decreased by 79% and 53%, respectively, compared with control. The antibiotics were sensitive to high temperature and were alkaline stable. The molecular weights of the substances were about 500-1000 Da. The bio-control efficiencies of the antibiotics had no significant difference with that of N43 cell suspension. It is a first report that B. pumilus strain produced oligopeptides which had inhibitory effect on R. solani Q1 at logarithmic growth phase. PMID:23417338

Two field isolates of Rhizoctonia solani were isolated from infected paddy plants in Malaysia. These isolates were verified via ITS-rDNA analysis that yielded ~720?bp products of the ITS1-5.8S-ITS4 region, respectively. The sequenced products showed insertion and substitution incidences which may result in strain diversity and possible variation in disease severity. These strains showed some regional and host-specific relatedness via Maximum Likelihood and further phylogenetic analysis via Maximum Parsimony showed that these strains were closely related to R. solani AG1-1A (with 99-100% identity). Subsequent to strain verification and analysis, these isolates were used in the screening of twenty rice varieties for tolerance or resistance to sheath blight via mycelial plug method where both isolates (1801 and 1802) showed resistance or moderate resistance to Teqing, TETEP, and Jasmine 85. Isolate 1802 was more virulent based on the disease severity index values. This study also showed that the mycelial plug techniques were efficient in providing uniform inoculum and humidity for screening. In addition this study shows that the disease severity index is a better mode of scoring for resistance compared to lesion length. These findings will provide a solid basis for our future breeding and screening activities at the institution. PMID:25258710

Rhizoctonia solani is an important soilborne and seedborne fungal pathogen of potato (Solanum tuberosum). The initial infection of sprouts prior to emergence causes lesions and may be lethal to the sprout or sprout tip, which results in initiation and compensatory growth of new sprouts. They emerge successfully and do not suffer significant damage. The mechanism behind this recovery phenomenon is not known. It was hypothesized that infection may induce pathogen defense in sprouts, which was investigated in the present study. Tubers were sprouted in cool and moist conditions in darkness to mimic conditions beneath soil. The basal portion of the sprout was isolated from the apical portion with a soft plastic collar and inoculated with highly virulent R. solani. Induction of defense-related responses was monitored in the apical portion using microarray and quantitative polymerase chain reaction techniques at 48 and 120 h postinoculation (hpi) and by challenge-inoculation with R. solani in two experiments. Differential expression of 122 and 779 genes, including many well-characterized defense-related genes, was detected at 48 and 120 hpi, respectively. The apical portion of the sprout also expressed resistance which inhibited secondary infection of the sprouts. The observed systemic induction of resistance in sprouts upon infection with virulent R. solani provides novel information about pathogen defense in potato before the plant emerges and becomes photosynthetically active. These results advance our understanding of the little studied subject of pathogen defense in subterranean parts of plants. PMID:18943407

The soilborne fungus Rhizoctonia solani anastomosis group 3 (AG-3PT) is a globally important potato pathogen. However, little is known about the population genetic processes affecting field populations of R. solani AG-3PT, especially in the South American Colombian Andes, which is near the center of diversity of the two most common groups of cultivated potato, Solanum tuberosum and S. phureja. We analyzed the genetic structure of 15 populations of R. solani AG-3PT infecting potato in Colombia using 11 simple-sequence repeat (SSR) markers. In total, 288 different multilocus genotypes were identified among 349 fungal isolates. Clonal fractions within field populations were 7 to 33%. RST statistics indicated a very low level of population differentiation overall, consistent with high contemporary gene flow, though moderate differentiation was found for the most distant southern populations. Genotype flow was also detected, with the most common genotype found widely distributed among field populations. All populations showed evidence of a mixed reproductive mode, including both asexual and sexual reproduction, but two populations displayed evidence of inbreeding. PMID:23464900

Bacillus subtilis RB14, which showed antibiotic activities against several phytopathogens in vitro by producing the antibiotics iturin A and surfactin, was subjected to a pot test to investigate its ability to suppress damping-off of tomato seedlings caused by Rhizoctonia solani. To facilitate recovery from soil, B. subtilis RB14-C, a spontaneous streptomycin-resistant mutant of RB14, was used. Damping-off was suppressed when the culture broth, cell suspension, or cell-free culture broth of RB14-C was inoculated into soil. Iturin A and surfactin were recovered from the soils inoculated with the cell suspension of RB14-C, confirming that RB14-C produced them in soil. The gene lpa-14, which was cloned from RB14 and required for the production of both antibiotics, was mutated in RB14-C, and a mutant, R(Delta)1, was constructed. The level of disease suppressibility of R(Delta)1 was low, but R(Delta)1(pC115), a transformant of R(Delta)1 with the plasmid pC115 carrying lpa-14, was restored in suppressibility. These results show that the antibiotics iturin A and surfactin produced by RB14 play a major role in the suppression of damping-off caused by R. solani. RB14-C, R(Delta)1, and R(Delta)1(pC115) persisted in soil during the experimental period and were recovered from the soil, mostly as spores. PMID:16535440

The necrotrophic soilborne fungal pathogens Rhizoctonia solani AG8 and R. oryzae are principal causal agents of Rhizoctonia root rot and bare patch of wheat in dryland cropping systems of the Pacific Northwest. A 3-year survey of 33 parcels at 11 growers' sites and 60 trial plots at 12 Washington State University cereal variety test locations was undertaken to understand the distribution of these pathogens. Pathogen DNA concentrations in soils, quantified using real-time polymerase chain reaction, were correlated with precipitation, temperature maxima and minima, and soil texture factors in a pathogen-specific manner. Specifically, R. solani AG8 DNA concentration was negatively correlated with precipitation and not correlated with temperature minima, whereas R. oryzae concentration was correlated with temperature minima but not with precipitation. However, both pathogens were more abundant in soils with higher sand and lower clay content. Principal component analysis also indicated that unique groups of meteorological and soil factors were associated with each pathogen. Furthermore, tillage did not affect R. oryzae but affected R. solani AG8 at P = 0.06. Lower soil concentrations of R. solani AG8 but not R. oryzae occurred when the previously planted crop was a broadleaf (P < 0.05). Our findings showed that R. solani AG8 concentrations were consistent with the general distribution of bare patch symptoms, based on field observations and surveys of other pathogens, but was present at many sites in which bare patch symptoms were not evident. Management of Rhizoctonia root rot and bare patch should account for the likelihood that each pathogen is affected by a unique group of agroecological variables. PMID:24915426

Lettuce belongs to the most commonly raw eaten food worldwide and its microbiome plays an important role for both human and plant health. Yet, little is known about the impact of potentially occurring pathogens and beneficial inoculants of the indigenous microorganisms associated with lettuce. To address this question we studied the impact of the phytopathogenic fungus Rhizoctonia solani and the biological control agent Bacillus amyloliquefaciens FZB42 on the indigenous rhizosphere and phyllosphere community of greenhouse-grown lettuce at two plant stages. The rhizosphere and phyllosphere gammaproteobacterial microbiomes of lettuce plants showed clear differences in their overall and core microbiome composition as well as in corresponding diversity indices. The rhizosphere was dominated by Xanthomonadaceae (48%) and Pseudomonadaceae (37%) with Rhodanobacter, Pseudoxanthomonas, Dokdonella, Luteimonas, Steroidobacter, Thermomonas as core inhabitants, while the dominating taxa associated to phyllosphere were Pseudomonadaceae (54%), Moraxellaceae (16%) and Enterobacteriaceae (25%) with Alkanindiges, Pantoea and a group of Enterobacteriaceae unclassified at genus level. The preferential occurrence of enterics in the phyllosphere was the most significant difference between both habitats. Additional enhancement of enterics on the phyllosphere was observed in bottom rot diseased lettuce plants, while Acinetobacter and Alkanindiges were identified as indicators of healthy plants. Interestingly, the microbial diversity was enhanced by treatment with both the pathogen, and the co-inoculated biological control agent. The highest impact and bacterial diversity was found by Rhizoctonia inoculation, but FZB42 lowered the impact of Rhizoctonia on the microbiome. This study shows that the indigenous microbiome shifts as a consequence to pathogen attack but FZB42 can compensate these effects, which supports their role as biocontrol agent and suggests a novel mode of action. PMID:24795707

Lettuce belongs to the most commonly raw eaten food worldwide and its microbiome plays an important role for both human and plant health. Yet, little is known about the impact of potentially occurring pathogens and beneficial inoculants of the indigenous microorganisms associated with lettuce. To address this question we studied the impact of the phytopathogenic fungus Rhizoctonia solani and the biological control agent Bacillus amyloliquefaciens FZB42 on the indigenous rhizosphere and phyllosphere community of greenhouse-grown lettuce at two plant stages. The rhizosphere and phyllosphere gammaproteobacterial microbiomes of lettuce plants showed clear differences in their overall and core microbiome composition as well as in corresponding diversity indices. The rhizosphere was dominated by Xanthomonadaceae (48%) and Pseudomonadaceae (37%) with Rhodanobacter, Pseudoxanthomonas, Dokdonella, Luteimonas, Steroidobacter, Thermomonas as core inhabitants, while the dominating taxa associated to phyllosphere were Pseudomonadaceae (54%), Moraxellaceae (16%) and Enterobacteriaceae (25%) with Alkanindiges, Pantoea and a group of Enterobacteriaceae unclassified at genus level. The preferential occurrence of enterics in the phyllosphere was the most significant difference between both habitats. Additional enhancement of enterics on the phyllosphere was observed in bottom rot diseased lettuce plants, while Acinetobacter and Alkanindiges were identified as indicators of healthy plants. Interestingly, the microbial diversity was enhanced by treatment with both the pathogen, and the co-inoculated biological control agent. The highest impact and bacterial diversity was found by Rhizoctonia inoculation, but FZB42 lowered the impact of Rhizoctonia on the microbiome. This study shows that the indigenous microbiome shifts as a consequence to pathogen attack but FZB42 can compensate these effects, which supports their role as biocontrol agent and suggests a novel mode of action. PMID:24795707

The effect of colonization with the vesicular-arbuscular mycorrhizal fungus Glomus etunicatum on the content of rishitin and solavetivone was determined in potato plants cv. Goldrush challenged with Rhizoctonia solani. Mycorrhization stimulated significantly the accumulation of both phytoalexins in roots of plantlets challenged with R. solani but did not influence phytoalexin levels in non-challenged plantlet roots. No accumulation of solavetivone or rishitin was detected in shoots. In Petri dish bioassays, rishitin and solavetivone inhibited mycelial growth of R. solani. PMID:14505123

Single-basidiospore isolates (SBIs) were obtained from field isolates of Thanatephorus cucumeris (Rhizoctonia solani) AG-1 IC and AG-2-2 IV. Formation of distinctive tufts, a recognized feature of heterokaryon synthesis, was observed, and isolates derived from hyphal-tipped tuft hyphae were obtained following pairings between various strains. Three distinctive types of tufts were formed: the fibrous type of mating-compatible homokaryon-homokaryon (Hom-Hom) pairings, the sparse type between heterokaryon-homokaryon (Het-Hom) pairings originating from one parent, and the compact type between Het-Hom pairings originating from different parents. Amplified Fragment Length Polymorphism (AFLP) profile of fingerprints of these tuft isolates verified that they were all heterokaryotic. Because of heterokaryotic vigor, the growth and pathogenicity of the majority of tuft isolates increased compared with their contributing SBIs. New somatic compatibility groups (SCGs) that were different from parental field isolates occurred following heterokaryon formation within T. cucumeris. Tuft isolates produced by Hom-Hom and Het-Hom pairings among isolates of different parents yielded no somatic compatibility with the original parent isolates and a high frequency of new SCGs (62–100%). This was in contrast to those produced by Hom-Hom and Het-Hom pairings among isolates with a common parent that yielded only 12–37% new SCGs. The SCG diversity of R. solani in the field may be attributed to new fitter heterokaryons formed between a heterokaryon of one pair of parents and a homokaryon of another parent pair. This mechanism greatly contributes to genetic diversity in the field and accounts for the failure to recover the expected distribution of SCGs from a field population. PMID:23995511

Field microplot, small plot, and greenhouse experiments were conducted to determine the effects of rotation crops on Pratylenchus penetrans, Meloidogyne hapla, and Rhizoctonia fragariae populations. Extraction of P. penetrans from roots and soil in microplots and field plots planted to rotation crops was highest for Garry oat, lowest for Triple S sorgho-sudangrass and Saia oat, and intermediate for strawberry, buckwheat, and canola. Isolation of R. fragariae from bait roots was highest for strawberry and canola after 2 years of rotation and lowest for Saia oat. Nematode extraction from roots of rotation crops in field soils was generally higher than from roots in microplots. Grasses were nonhosts of M. hapla. Strawberry, canola, and buckwheat supported root-knot populations over time, but there were no differences in nematode numbers regardless of crop after one season of strawberry growth. Garry oat, canola, and, to a lesser extent, buckwheat supported large populations of P. penetrans without visible root symptoms. Strawberry plants supported fewer nematodes due to root damage. Nematode numbers from soil were less than from roots for all crops. While there were similar trends for pathogen recovery after more than 1 year of strawberry growth following rotation, differences in pathogen density and fruit yield were not significant. In the greenhouse, P. penetrans populations in roots and soil in pots were much higher for Garry oat than for Saia oat. Total P. penetrans adult and juvenile numbers per pot ranged from 40 to 880 (mean = 365.6) for Garry oat and 0 to 40 (mean = 8.7) for Saia oat. Production of Saia oat as a rotation crop may be a means of managing strawberry nematodes and black root rot in Connecticut. PMID:19270931

Single-basidiospore isolates (SBIs) were obtained from field isolates of Thanatephorus cucumeris (Rhizoctonia solani) AG-1 IC and AG-2-2 IV. Formation of distinctive tufts, a recognized feature of heterokaryon synthesis, was observed, and isolates derived from hyphal-tipped tuft hyphae were obtained following pairings between various strains. Three distinctive types of tufts were formed: the fibrous type of mating-compatible homokaryon-homokaryon (Hom-Hom) pairings, the sparse type between heterokaryon-homokaryon (Het-Hom) pairings originating from one parent, and the compact type between Het-Hom pairings originating from different parents. Amplified Fragment Length Polymorphism (AFLP) profile of fingerprints of these tuft isolates verified that they were all heterokaryotic. Because of heterokaryotic vigor, the growth and pathogenicity of the majority of tuft isolates increased compared with their contributing SBIs. New somatic compatibility groups (SCGs) that were different from parental field isolates occurred following heterokaryon formation within T. cucumeris. Tuft isolates produced by Hom-Hom and Het-Hom pairings among isolates of different parents yielded no somatic compatibility with the original parent isolates and a high frequency of new SCGs (62-100%). This was in contrast to those produced by Hom-Hom and Het-Hom pairings among isolates with a common parent that yielded only 12-37% new SCGs. The SCG diversity of R. solani in the field may be attributed to new fitter heterokaryons formed between a heterokaryon of one pair of parents and a homokaryon of another parent pair. This mechanism greatly contributes to genetic diversity in the field and accounts for the failure to recover the expected distribution of SCGs from a field population. PMID:23995511

Anastomosis group 3 (AG-3) of Rhizoctonia solani (teleomorph = Thanatephorus cucumeris) is frequently associated with diseases of potato (AG-3 PT) and tobacco (AG-3 TB). Although isolates of R. solani AG-3 from these two Solanaceous hosts are somatically related based on anastomosis reaction and taxonomically related based on fatty acid, isozyme and DNA characters, considerable differences are evident in their biology, ecology, and epidemiology. However, genetic diversity among field populations of R. solani AG-3 PT and TB has not been documented. In this study, the genetic diversity of field populations of R. solani AG-3 PT and AG-3 TB in North Carolina was examined using somatic compatibility and amplified fragment length polymorphism (AFLP) criteria. A sample of 32 isolates from potato and 36 isolates from tobacco were paired in all possible combinations on PDA plus activated charcoal and examined for their resulting somatic interactions. Twenty-eight and eight distinct somatic compatibility groups (SCG) were identified in the AG-3 PT and AG-3 TB samples, respectively. AFLP analyses indicated that each of the 32 AG-3 PT isolates had a distinct AFLP phenotype, whereas 28 AFLP phenotypes were found among the 36 isolates of AG-3 TB. None of the AG-3 PT isolates were somatically compatible or shared a common AFLP phenotype with any AG-3 TB isolate. Clones (i.e., cases where two or more isolates were somatically compatible and shared the same AFLP phenotype) were identified only in the AG-3 TB population. Four clones from tobacco represented 22% of the total population. All eight SCG from tobacco were associated with more than one AFLP phenotype. Compatible somatic interactions between AG-3 PT isolates occurred only between certain isolates from the same field (two isolates in each of four different fields), and when this occurred AFLP phenotypes were similar but not identical. PMID:21156515

The ability of yeasts to attach to hyphae or conidia of phytopathogenic fungi has been speculated to contribute to biocontrol activity on plant surfaces. Attachment of phylloplane yeasts to Botrytis cinerea, Rhizoctonia solani, and Sclerotinia homoeocarpa was determined using in vitro attachment assays. Yeasts were incubated for 2 d on potato dextrose agar (PDA) prior to experimentation. A total of 292 yeasts cultured on PDA were screened for their ability to attach to conidia of B. cinerea; 260 isolates (89.1%) attached to conidia forming large aggregates of cells, and 22 isolates (7.5%) weakly attached to conidia with 1 or 2 yeast cells attached to a few conidia. Ten yeasts (3.4%), including 8 isolates of Cryptococcus laurentii, 1 isolate of Cryptococcus flavescens, and an unidentified species of Cryptococcus, failed to attach to conidia. All non-attaching yeasts produced copious extracellular polysaccharide (EPS) on PDA. Seventeen yeast isolates did not attach to hyphal fragments of B. cinerea, R. solani, and S. homoeocarpa after a 1 h incubation, but attachment was observed after 24 h. Culture medium, but not culture age, significantly affected the attachment of yeast cells to conidia of B. cinerea. The 10 yeast isolates that did not attach to conidia when grown on agar did attach to conidia (20%-57% of conidia with attached yeast cells) when cultured in liquid medium. Attachment of the biocontrol yeast Rhodotorula glutinis PM4 to conidia of B. cinerea was significantly greater at 1 x 10(7) yeast cells x mL(-1) than at lower concentrations of yeast cells. The ability of yeast cells to attach to fungal conidia or hyphae appears to be a common phenotype among phylloplane yeasts. PMID:15714235

Belowground symptoms of sugar beet caused by the beet cyst nematode (BCN) Heterodera schachtii include the development of compensatory secondary roots and beet deformity, which, thus far, could only be assessed by destructively removing the entire root systems from the soil. Similarly, the symptoms of Rhizoctonia crown and root rot (RCRR) caused by infections of the soil-borne basidiomycete Rhizoctonia solani require the same invasive approach for identification. Here nuclear magnetic resonance imaging (MRI) was used for the non-invasive detection of belowground symptoms caused by BCN and/or RCRR on sugar beet. Excessive lateral root development and beet deformation of plants infected by BCN was obvious 28 days after inoculation (dai) on MRI images when compared with non-infected plants. Three-dimensional images recorded at 56 dai showed BCN cysts attached to the roots in the soil. RCRR was visualized by a lower intensity of the MRI signal at sites where rotting occurred. The disease complex of both organisms together resulted in RCRR development at the site of nematode penetration. Damage analysis of sugar beet plants inoculated with both pathogens indicated a synergistic relationship, which may result from direct and indirect interactions. Nuclear MRI of plants may provide valuable, new insight into the development of pathogens infecting plants below- and aboveground because of its non-destructive nature and the sufficiently high spatial resolution of the method. PMID:21948851

Although Rhizoctonia solani is a cosmopolitan soilborne pathogen, the genus includes isolates with different pathogenicity ranging from high virulence to avirulence. The biocontrol strain Pseudomonas fluorescens P190r and the arbuscular mycorrhizal (AM) fungus Glomus mosseae BEG12 were inoculated alone or in combination in tomato plants infested by the mildly virulent pathogen R. solani #235. Plant growth as well as root

Disease suppressiveness against Rhizoctonia solani AG 2-1 in cauliflower was studied in two marine clay soils with a sandy loam texture. The soils had a different cropping history. One soil had a long-term (40 years) cauliflower history and was suppressive, the other soil was conducive and came from a pear orchard not having a cauliflower crop for at least 40

Rhizoctonia solani is a soil-borne basidiomycete fungus with a necrotrophic lifestyle which is classified into fourteen reproductively incompatible anastomosis groups (AGs). One of these, AG8, is a devastating pathogen causing bare patch of cereals, brassicas and legumes. R. solani is a multinucleate heterokaryon containing significant heterozygosity within a single cell. This complexity posed significant challenges for the assembly of its genome. We present a high quality genome assembly of R. solani AG8 and a manually curated set of 13,964 genes supported by RNA-seq. The AG8 genome assembly used novel methods to produce a haploid representation of its heterokaryotic state. The whole-genomes of AG8, the rice pathogen AG1-IA and the potato pathogen AG3 were observed to be syntenic and co-linear. Genes and functions putatively relevant to pathogenicity were highlighted by comparing AG8 to known pathogenicity genes, orthology databases spanning 197 phytopathogenic taxa and AG1-IA. We also observed SNP-level “hypermutation” of CpG dinucleotides to TpG between AG8 nuclei, with similarities to repeat-induced point mutation (RIP). Interestingly, gene-coding regions were widely affected along with repetitive DNA, which has not been previously observed for RIP in mononuclear fungi of the Pezizomycotina. The rate of heterozygous SNP mutations within this single isolate of AG8 was observed to be higher than SNP mutation rates observed across populations of most fungal species compared. Comparative analyses were combined to predict biological processes relevant to AG8 and 308 proteins with effector-like characteristics, forming a valuable resource for further study of this pathosystem. Predicted effector-like proteins had elevated levels of non-synonymous point mutations relative to synonymous mutations (dN/dS), suggesting that they may be under diversifying selection pressures. In addition, the distant relationship to sequenced necrotrophs of the Ascomycota suggests the R. solani genome sequence may prove to be a useful resource in future comparative analysis of plant pathogens. PMID:24810276

ABSTRACT Peat moss-based potting mix was amended with either of two composted swine wastes, CSW1 and CSW2, at rates from 4 to 20% (vol/vol) to evaluate suppression of pre-emergence damping-off of impatiens (Impatiens balsamina) caused by Rhizoctonia solani (anastomosis group-4). A cucumber bioassay was used prior to each impatiens experiment to monitor maturity of compost as the compost aged in a curing pile by evaluating disease suppression toward both Pythium ultimum and R. solani. At 16, 24, 32, and 37 weeks after composting, plug trays filled with compost-amended potting mix were seeded with impatiens and infested with R. solani to determine suppression of damping-off. Pre-emergence damping-off was lower for impatiens grown in potting mix amended with 20% CSW1 than in CSW2-amended and nonamended mixes. To identify relationships between disease suppression and microbial parameters, samples of mixes were collected to determine microbial activity, biomass carbon and nitrogen, functional diversity, and population density. Higher rates of microbial activity were observed with increasing rates of CSW1 amendment than with CSW2 amendments. Microbial biomass carbon and nitrogen also were higher in CSW1-amended mixes than in CSW2-amended potting mixes 1 day prior to seeding and 5 weeks after seeding. Principal component analysis of Biolog-GN2 profiles showed different functional diversities between CSW1- and CSW2-amended mixes. Furthermore, mixes amended with CSW1 had higher colony forming units of fungi, endospore-forming bacteria, and oligotrophic bacteria. Our results suggest that enhanced microbial activity, functional and population diversity of stable compost-amended mix were associated with suppressiveness to Rhizoctonia damping-off in impatiens. PMID:18944095

Ceratobasidium includes orchid mycorrhizal symbionts, plant pathogens and biocontrol agents of soilborne plant pathogens. It is not known to what extent members of the first guild also can participate in the others. Ceratobasidium spp. were isolated from roots of Colombian orchids and identified by phylogeny based on nrITS sequences. Phylogenetic grouping of Ceratobasidium spp. isolates corresponded to orchid host substrate (epiphytic vs. terrestrial). Isolates were tested for virulence on rice and for biocontrol of Rhizoctonia solani, causal agent of sheath blight of rice. All Ceratobasidium spp. isolates caused some signs of sheath blight but significantly less than a pathogenic R. solani used as a positive control. When Ceratobasidium spp. isolates were inoculated on rice seedlings 3 d before R. solani, they significantly reduced disease expression compared to controls inoculated with R. solani alone. The use of Ceratobasidium spp. from orchids for biological control is novel, and biodiverse countries such as Colombia are promising places to look for new biocontrol agents. PMID:22962357

Biological control using antagonistic microbes to minimize the use of chemical pesticides has recently become more prevalent. In an attempt to find an integrated control system for sheath blight, caused by Rhizoctonia solani in rice, Streptomyces philanthi RM-1-138, commercial formulations of Bacillus subtilis as Larminar® and B. subtilis strain NSRS 89-24+MK-007 as Biobest® and chemical fungicides including carbendazim®, validamycin®, propiconazole® and mancozeb® were applied alone and in combination with S. philanthi RM-1-138. In vitro experiments showed that all treatments tested did provide some control against mycelial growth and sclerotia production by R. solani PTRRS-9. In addition, the four chemical fungicides had no detrimental effects on S. philanthi RM-1-138 even at high concentrations (up to 100 ?g/ml). The efficacy of S. philanthi RM-1-138, the commercial formulations of B. subtilis, chemical fungicides alone or in combination with S. philanthi RM-1-138 was also tested in a greenhouse experiment against sheath blight disease on rice plants. All treatments showed some protection of rice for sheath blight by 47-60 % when carbendazim® was applied alone and up to 74 % when combined with S. philanthi RM-1-138. PMID:23653261

The effects of inundative releases of entomopathogenic Steinernema carpocapsae and S. feltiae infective juveniles and applications of the biological control fungus Trichoderma harzianum T-22 (RootShield) on Pratylenchus penetrans and strawberry black root rot caused by Rhizoctonia fragariae were determined in field microplots and small plots. Entomopathogenic nematodes were applied as a soil drench at rates of 7.4 or 14.8 billion per ha in May or August for 3 years. RootShield was applied as crown dips at planting or later as a soil drench. There were no differences in P. penetrans from plants drenched with water alone or with S. carpocapsae or S. feltiae nematodes, averaged over rates and timing. The nematode species applied and the rate or timing of application had no effect on lesion nematodes. Our results suggest that P. penetrans exposure to living or heat-killed S. feltiae and associated bacteria resulted in temporary lack of motility. A progressively increasing proportion of P. penetrans became active again and, after 8 days, had infected tomato roots in similar numbers to unexposed P. penetrans. In laboratory assays and field plots or microplots, S. carpocapsae and S. feltiae did not permanently affect P. penetrans in tomato or strawberry. PMID:19265955

Rhizoctonia solani is an important soilborne pathogen of potato plants whose control typically depends on chemicals. Here, we screened six fungal endophytes for the suppression of R. solani growth both in vitro and in a greenhouse. These isolates were identified using morphology and internal transcribed spacer regions of rDNA as Alternaria longipes, Epicoccum nigrum, Phomopsis sp., and Trichoderma atroviride. Both T. atroviride and E. nigrum showed significant in vitro inhibition of mycelial growth of R. solani, with the greatest inhibition zone observed for E. nigrum species in dual cultures. The highest inhibition was observed for T. atroviride. The inhibition rate was also significantly correlated with the culture filtrates of these isolates. Confocal microscopy showed that T. atroviride acts as a mycoparasite and competitor. However, E. nigrum and A. longipes produce secondary metabolites, while Phomospsis sp. competes for nutrients and space. Greenhouse experiments confirmed that T. atroviride and E. nigrum improved potato yield significantly and decreased the stem disease severity index of sensitive potato. PMID:20738401

ABSTRACT Isolates of Rhizoctonia solani collected from mycorrhizal orchid (Pterostylis acuminata) plants and adjacent leaf litter were characterized. Of 23 selected isolates, 20 were members of a new anastomosis group (AG-12) and the rest were members of AG-6. There were no bridging anastomosis reactions observed between AG-12 and other AGs of R. solani. Among the 20 isolates of AG-12 evaluated, 18 vegetatively compatible populations were detected, indicating diversity within the AG. Mature cultures were dark brown, as were mature sclerotia. Some cultures produced alternating dark- and light-colored concentric rings, with sclerotia forming in the darker rings. Most cultures were appressed to the agar surface. In tests run to characterize pathogenic potential, selected mycorrhizal isolates of AG-12 and AG-6 did little damage to potato and barley seedlings, moderate damage to head lettuce seedlings, and more extensive damage to seedlings of cauliflower and radish. Isolates of AG-12 have not been observed to fruit in nature, and all attempts to induce formation of the teleomorph (Thanatephorus cucumeris) in the laboratory by selected isolates of AG-12 failed. PMID:18944739

Rhizoctonia solani is an important soil-borne necrotrophic fungal pathogen, with a broad host range and little effective resistance in crop plants. Arabidopsis is resistant to R. solani AG8 but susceptible to R. solani AG2-1. A screen of 36 Arabidopsis ecotypes and mutants affected in the auxin, camalexin, salicylic acid, abscisic acid and ethylene/jasmonic acid pathways did not reveal any variation in response to R. solani and demonstrated that resistance to AG8 was independent of these defense pathways. The Arabidopsis Affymetrix ATH1 Genome array was used to assess global gene expression changes in plants infected with AG8 and AG2-1 at seven days post-infection. While there was considerable overlap in the response, some gene families were differentially affected by AG8 or AG2-1 and included those involved in oxidative stress, cell wall associated proteins, transcription factors and heat shock protein genes. Since a substantial proportion of the gene expression changes were associated with oxidative stress responses, we analysed the role of NADPH oxidases in resistance. While single NADPH oxidase mutants had no effect, a NADPH oxidase double mutant atrbohf atrbohd resulted in an almost complete loss of resistance to AG8, suggesting that reactive oxidative species play an important role in Arabidopsis's resistance to R. solani. PMID:23451091

This work aims to characterize the bioactive molecules produced by an antagonistic Bacillus sp. strain BCLRB2 isolated from healthy leaves of olive tree against Rhizoctonia solani and Sclerotinia sclerotiorum. The bacterial strain isolated showed a high and persistent antifungal activity against the two pathogens. The free-cell supernatant showed also a high antifungal activity against R. solani and at a lower extent against S. sclerotiorum. The partial purification of the antifungal substances with methanol gradient applied to C18 column binding the Bacillus BCLRB2 culture supernatant showed that the 20% and 60% methanol fractions had a high and specific activity against S. sclerotiorum and R. solani, respectively. The mass spectrometry identification of the compounds in the fraction specifically active against S. sclerotiorum revealed the presence of bacillomycin D C16 as a major lipopeptide. The fraction specifically active against R. solani contained bacillomycin D C15 and 2 unknown lipopeptides. The 80% methanol fraction had a moderate and a broad spectrum activity against the two pathogens and consisted from two iturin D (C13 and C14) as a major lipopeptides. PMID:25272736

A binucleate Rhizoctonia (BNR) species was isolated from a clay loam soil on the Epoisses experimental station of INRA, Dijon and identified as belonging to the anastomosis Group A (AG-A). The BNR was inoculated to a Myc- Pisum sativum mutant (P53, sym30 locus) and its wild-type parent (cv Frisson) in the presence or absence of the arbuscular mycorrhizal fungus Glomus mosseae. The BNR had no significant effect on plant weight. Myc+ and Myc- roots were equally susceptible towards BNR and showed no localized cellular defense responses. The presence of BNR decreased significantly the percentage of root length colonized by G. mosseae and, inversely, G. mosseae reduced the number of BNR monilioid chains formed in root epidermal cells of the two pea genotypes. The pisatin concentration was increased significantly by BNR in both Myc+ and Myc- roots and by G. mosseae in the wild-type pea plants. The highest accumulation of pisatin was observed in Myc+ roots when both fungi were present. PMID:12035734

A growth-chamber experiment was conducted to determine how foliar disease or wounding affects the ability of 2 phylloplane yeasts (Rhodotorula glutinis and Cryptococcus laurentii) to colonize leaves of tall fescue (Festuca arundinacea). Yeasts were applied separately and together onto healthy leaves, leaves infected with Rhizoctonia solani (diseased), and mechanically bruised (wounded) leaves. In all 3 trials, the leaf disturbance treatment significantly affected the abundance of yeast on the phylloplane of tall fescue. Yeast abundance on the diseased or wounded leaves was significantly greater than on the nontreated, healthy leaves. In 2 of the 3 trials, the yeast species applied also had a significant affect on yeast abundance. Typically, R. glutinis was significantly more abundant than C. laurentii when applied individually, but not significantly greater than the total yeast colony-forming units of the co-inoculated treatment. When the 2 yeasts were co-inoculated onto the leaves, R. glutinis comprised 89.7%, 75.4%, and 67.6% of the recovered yeast colony-forming units on healthy, diseased, and wounded leaves, respectfully. Our data suggest that these 2 species of yeasts will differentially colonize compromised leaf tissue with disease or wounds favoring populations of R. glutinis over C. laurentii. PMID:19935888

The complexity of plant-pathogen interactions makes their dissection a challenging task for metabolomics studies. Here we are reporting on an integrated metabolomics networking approach combining gas chromatography/mass spectrometry (GC/MS) with Fourier transform ion cyclotron resonance/mass spectrometry (FT-ICR/MS) and bioinformatics analyses for the study of interactions in the potato sprout-Rhizoctonia solani pathosystem and the fluctuations in the global metabolome of sprouts. The developed bioanalytical and bioinformatics protocols provided a snapshot of the sprout's global metabolic network and its perturbations as a result of pathogen invasion. Mevalonic acid and deoxy-xylulose pathways were substantially up-regulated leading to the biosynthesis of sesquiterpene alkaloids such as the phytoalexins phytuberin, rishitin, and solavetivone, and steroidal alkaloids having solasodine and solanidine as their common aglycons. Additionally, the perturbation of the sprout's metabolism was depicted in fluctuations of the content of their amino acids pool and that of carboxylic and fatty acids. Components of the systemic acquired resistance (SAR) and hypersensitive reaction (HR) such as azelaic and oxalic acids were detected in increased levels in infected sprouts and strategies of the pathogen to overcome plant defense were proposed. Our metabolic approach has not only greatly expanded the multitude of metabolites previously reported in potato in response to pathogen invasion, but also enabled the identification of bioactive plant-derived metabolites providing valuable information that could be exploited in biotechnology, biomarker-assisted plant breeding, and crop protection for the development of new crop protection agents. PMID:22880040

Sheath blight disease, caused by Rhizoctonia solani 1802/KB was screened on two rice varieties, Oryza sativaindica cultivar MR219 and Oryza sativa indica cultivar UKMRC9. The disease symptom was severe in MR219 compared to UKMRC9. Total RNA from R. solani 1802/KB, infected rice leaves of MR219 and infected rice leaves of UKMRC9 were extracted using TRIzol reagent, purified and sent for small RNA sequencing. Three miRNA libraries were generated and analyzed. The libraries generated 65 805, 78 512 and 81 325 known miRNAs respectively. The structure of miRNA of these samples was predicted. The up-regulated and down-regulated of miRNAs target gene prediction and its target functions were discovered and were mainly related to the growth and development of metabolism, protein transport, transcriptional regulation, stress response, and hormone signaling and electron transfer. Sheath blight-induced differential expression of known miRNAs tends to targetMYB transcription factor, F-box proteins, NBS-LRR, leucine-rich repeat receptor protein kinases and zinc finger proteins. Detecting new miRNAs and measuring the expression profiles of known miRNAs is an important tasks required for a better understanding of various biological conditions. Therefore, further analysis using Gene Ontology Slim will be conducted to deduce some biological information from the datasets obtained.

ABSTRACT The induction of disease-suppressive soils in response to specific cropping sequences has been demonstrated for numerous plant-pathogen systems. The role of host genotype in elicitation of the essential transformations in soil microbial community structure that lead to disease suppression has not been fully recognized. Apple orchard soils were planted with three successive 28-day cycles of specific wheat cultivars in the greenhouse prior to infestation with Rhizoctonia solani anastomosis group (AG)-5 or AG-8. Suppressiveness to Rhizoctonia root rot of apple caused by the introduced isolate of R. solani AG-5 was induced in a wheat cultivar-specific manner. Pasteurization of soils after wheat cultivation and prior to pathogen introduction eliminated the disease suppressive potential of the soil. Wheat cultivars that induced disease suppression enhanced populations of specific fluorescent pseudomonad genotypes with antagonistic activity toward R. solani AG-5 and AG-8, but cultivars that did not elicit a disease suppressive soil did not modify the antagonistic capacity of this bacterial community. When soils were infested prior to the initial wheat planting, all cultivars were uniformly susceptible to R. solani AG-8. However, when pathogen inoculum was added after three growth-cycles, wheat root infection during the fourth growth-cycle varied in a cultivar specific manner. The same wheat cultivar-specific response in terms of transformation of the fluorescent pseudomonad community and subsequent suppression of Rhizoctonia root rot of apple was observed in three different orchard soils. These results demonstrate the importance of host genotype in modification of indigenous saprophytic microbial communities and suggest an important role for host genotype in the success of biological control. PMID:18943884

1-Hydroxyphenazine (1-OH-PHZ), a natural product from Pseudomonas aeruginosa strain SD12, was earlier reported to have potent antifungal activity against Rhizoctonia solani. In the present work, the antifungal activity of 1-OH-PHZ on 40S ribosomal S9 protein was validated by molecular docking approach. 1-OH-PHZ showed interaction with two polar contacts with residues, Arg69 and Phe19, which inhibits the synthesis of fungal protein. Our study reveals that 1-OH-PHZ can be a potent inhibitor of 40S ribosomal S9 protein of R. solani that may be a promising approach for the management of fungal diseases. PMID:24864254

The objective of this work was to investigate the ability of the plant growth-promoting rhizobacterium Pseudomonas aureofaciens 63-28 to induce plant defense systems, including defense-related enzyme levels and expression of defense-related isoenzymes, and isoflavone production, leading to improved resistance to the phytopathogen Rhizoctonia solani AG-4 in soybean seedlings. Seven-dayold soybean seedlings were inoculated with P. aureofaciens 63-28, R. solani AG-4, or P. aureofaciens 63-28 plus R. solani AG-4 (P+R), or not inoculated (control). After 7 days of incubation, roots treated with R. solani AG-4 had obvious damping-off symptoms, but P+R-treated soybean plants had less disease development, indicating suppression of R. solani AG-4 in soybean seedlings. Superoxide dismutase (SOD) and catalase (CAT) activities of R. solani AG-4-treated roots increased by 24.6% and 54.0%, respectively, compared with control roots. Ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) activities of R. solani AG-4-treated roots were increased by 75.1% and 23.6%, respectively. Polyphenol oxidase (PPO) activity in soybean roots challenged with P. aureofaciens 63-28 and P+R increased by 25.0% and 11.6%, respectively. Mn-SOD (S1 band on gel) and Fe-SOD (S2) were strongly induced in P+R-treated roots, whereas one CAT (C1) and one APX (A3) were strongly induced in R. solani AG-4- treated roots. The total isoflavone concentration in P+Rtreated shoots was 27.2% greater than the control treatment. The isoflavone yield of R. solani AG-4-treated shoots was 60.9% less than the control. PMID:21532321

An endophytic bacterium, Bacillus thuringiensis GS1, was isolated from bracken (Pteridium aquilinum) and found to have maximal production of chitinase (4.3 units/ml) at 5 days after culture. This study investigated the ability of B. thuringiensis GS1 to induce resistance to Rhizoctonia solani KACC 40111 (RS) in cucumber plants. Chitinase activity was greatest in RS-treated plants at 4 days. beta-1,3- Glucanase activity was highest in GS1-treated plants at 5 days. Guaiacol peroxidase (GPOD) activity increased continuously in all treated plants for 5 days. Ascorbate peroxidase (APX) activity in RS-treated plants was increased 1.5-fold compared with the control at 4 days. Polyphenol oxidase (PPO) activity in RS-treated plants was increased 1.5-fold compared with the control at 3 days. At 5 days after treatment, activity staining revealed three bands with chitinase activity (Ch1, Ch2, and Ch3) on SDSPAGE of cucumber plants treated with GS1+RS, whereas only one band was observed for RS-treated plants (Ch2). One GPOD isozyme (Gp1) was also observed in response to treatment with RS and GS1+RS at 4 days. One APX band (Ap2) was present on the native-PAGE gel of the control, and GS1- and GS1+RS-treated plants at 1 day. PPO bands (Po1 and Po2) from RS- and GS1+RS-treated plants were stronger than in the control and GS1-treated plants upon native-PAGE at 5 days. Taken together, these results indicate that the induction of PR proteins and defense-related enzymes by B. thuringiensis GS1 might have suppressed the damping-off caused by R. solani KACC 40111 in cucumber plants. PMID:22450798

The destructive soil-borne plant pathogenic basidiomycetous fungus Thanatephorus cucumeris (Frank) Donk [anamorph: Rhizoctonia solani Kühn] is not a homogeneous species, but is composed of at least twelve anastomosis groups (AG), which seem to be genetically isolated. The genetics of several T. cucumeris anastomosis groups has been studied by analysis of heterokaryotic tuft formation in the area of contact between homokaryotic single-spore isolates, revealing that AG 1 is heterokaryotic and bipolar. To prove that tuft formation is due to heterokaryosis, AFLP DNA fingerprinting has been applied to a heterokaryotic T. cucumeris AG 1-IC isolate, its homokaryotic single spore-derived progeny, and newly formed heterokaryons. By means of AFLP markers, it is demonstrated that fluffy tufts formed upon pairing of homokaryons from different mating types are newly formed heterokaryons. Mating type-correlated markers have also been found, which will be useful for future studies of the genetics of this fungal species complex. PMID:9987848

A rapid identification assay for Waitea circinata (anamorph: Rhizoctonia spp.) varieties zeae and circinata causing patch diseases on turfgrasses was developed based on the universally primed PCR (UP-PCR) products cross-blot hybridization. Tester isolates belonging to the two varieties of W. circinata were amplified with a single UP primer L21, which generated multiple DNA fragments for each variety. Probes were prepared with UP-PCR products of each tester isolate by labeling with digoxigenin. Fieldcollected W. circinata isolates and representative isolates of different R. solani anastomosis groups (AG) and AG subgroups were amplified with L21, immobilized on nylon membrane and cross hybridized with the two probes. Isolates within a W. circinata variety cross-hybridized strongly, while non-homologous isolates did not cross-hybridize or did so weakly. Closely related W. circinata varieties zeae and circinata were clearly distinguished with this assay. Sequence-characterized amplified region (SCAR) markers also were developed from UP-PCR products to identify isolates of Thanatephorus cucumeris (anamorph: R. solani) AG 1-IB and AG 2-2IIIB. These two AGs are commonly isolated from diseased, cool-season turfgrasses. The specific SCAR markers that were developed could differentiate isolates of AG 1-IB or AG 2-2IIIB groups. These SCAR markers did not amplify a product from genomic DNA of nontarget isolates of Rhizoctonia. The specificities and sensitivities of the SCAR primers were tested on total DNA extracted from several field-grown, cool-season turf species having severe brown-patch symptoms. First, the leaf samples from diseased turf species were tested for the anastomosis groups of the causal pathogen, and thereafter the total DNA was amplified with the specific primers. The specific primers were sensitive and unique enough to produce a band from total DNA of diseased turfgrasses infected with either AG 1-IB or AG 2-2IIIB. PMID:24396105

ABSTRACT A murine hybridoma cell line GD2 secreting an immunoglobulin (Ig)M monoclonal antibody (MAb) was produced against surface antigens from an anastomosis group (AG) 4 isolate of Rhizoctonia solani (teleomorph: Thanatephorus cucumeris). Ascites were produced in mice using GD2 hybridoma cells and used to develop a rapid immunochromatographic lateral flow device (LFD) for the detection of antigens from R. solani and certain related Rhizoctonia spp. The LFD was tested for specificity against surface antigens from related and unrelated soil fungi. Antigens from representative isolates of R. solani AGs 1, 2-1, 2-3, 2-t, 3, 4, 5, 6, 7, 8, 9, 10, 11, and BI gave a positive response in LFD tests, as did antigens from Thanatephorus orchidicola, T. praticola, R. fragariae (teleomorph: Ceratorhiza fragariae), Ceratorhiza goodyerae-repentis, Ceratobasidium cornigerum, and binucleate AGE. Antigens from R. solani AGs 2-2, 2-2IIIB, and 2-2IV and from the related fungi R. carotae, R. cerealis (teleomorph: Ceratobasium cereale), R. crocorum (teleomorph: Helicobasidium brebissonii), R. oryzae (teleomorph Waitea circinata), and R. zeae gave negative responses, as did antigens from a range of unrelated fungi and oomycetes including Fusarium, Gliocladium, Trichoderma, Pythium, and Phytophthora spp. The usefulness of the LFD to detect R. solani was demonstrated in soils naturally infested with R. solani AG3. There was close agreement between results of LFD tests and conventional plate enrichment tests employing selective medium. The specificity of the technique was confirmed by polymerase chain reaction PCR using R. solani AG3-specific primers and by analyses based on sequences of the internal transcribed spacer (ITS)1-5.8S-ITS2 rRNA-encoding regions of unrelated fungi recovered from soil samples. The LFD was used to quantify R. solani AG4 in artificially infested soil samples (chopped potato soil inoculum). Estimates of CFU per gram of soil were derived using a most-probable number technique, which was based on the presence or absence of a detectable signal in the LFD. Estimates of CFU obtained in LFD tests and those obtained in a plate-trapped antigen enzyme-linked immunosorbent assay incorporating MAb GD2 were identical (449 CFU g(-1) of soil). PMID:18943976

Genetic manipulation of fluorescent pseudomonads has provided major insight into their production of antifungal molecules and their role in biological control of plant disease. Burkholderia cepacia also produces antifungal activities, but its biological control activity is much less well characterized, in part due to difficulties in applying genetic tools. Here the authors report genetic and biochemical characterization of a soil isolate of B. cepacia relating to its production of an unusual antibiotic that is very active against a variety of soil fungi. Purification and preliminary structural analyses suggest that this antibiotic (called AFC-BC11) is a novel lipopeptide associated largely with the cell membrane. Analysis of conditions for optimal production of AFC-BC11 indicated stringent environmental regulation of its synthesis. Furthermore, the authors show that production of AFC-BC11 is largely responsible for the ability of B. cepacia BC11 to effectively control the damping-Off of cotton caused by the fungal pathogen Rhizoctonia solani in a gnotobiotic system. Using Tn5 mutagenesis, they identified, cloned, and characterized a region of the genome of strain BC11 that is required for production of this antifungal metabolite. DNA sequence analysis suggested that this region encodes proteins directly involved in the production of a nonribosomally synthesized lipopeptide.

A two-step method was developed to evaluate potato resistance to black scurf caused by Rhizoctonia solani. Tuber piece inoculum was first conducted in the laboratory, which was also first reported in this study. After inoculation with pathogen discs and culture for 48 h, the necrotic spots on the inoculated potato pieces were generated and measured by the crossing method. Further evaluation was conducted through field experiments using a wheat bran inoculum method. The wheat bran inoculum was placed into the pit dispersedly and surrounded seed tubers. Each cultivar or line was subjected to five treatments of 0-, 2-, 3-, 4-, and 5-g soil inoculum. The results showed that 2–4 g of wheat bran inoculum was the optimum for identifying tuber black scurf resistance. The laboratory scores positively correlated with the incidence and severity of black scurf in the field. According to the results in the laboratory, relatively resistant cultivars could be selected for further estimation of tuber black scurf resistance in field experiments. It is a practical and effective screening method for rapid identification of resistant potato germplasm, which can reduce workload in the field, shorten time required for identification. PMID:24987302

A series of multilocus sequence-based nuclear DNA markers was developed to infer the phylogeographical history of the Basidiomycetous fungal pathogen Rhizoctonia solani AG-1 IA infecting rice and soybean worldwide. The strategy was based on sequencing of cloned genomic DNA fragments (previously used as RFLP probes) and subsequent screening of fungal isolates to detect single nucleotide polymorphisms (SNPs). Ten primer pairs were designed based on these sequences, which resulted in PCR amplification of 200-320 bp size products and polymorphic sequences in all markers analyzed. By direct sequencing we identified both homokaryon and heterokaryon (i.e. dikaryon) isolates at each marker. Cloning the PCR products effectively estimated the allelic phase from heterokaryotic isolates. Information content varied among markers from 0.5 to 5.9 mutations per 100 bp. Thus, the former RFLP codominant probes were successfully converted into six distinctively variable sequence-based nuclear DNA markers. Rather than discarding low polymorphism loci, the combination of these distinctively variable anonymous nuclear markers would constitute an asset for the unbiased estimate of the phylogeographical parameters such as population sizes and divergent times, providing a more reliable species history that shaped the current population structure of R. solani AG-1 IA. PMID:21637462

Genetic manipulation of fluorescent pseudomonads has provided major insight into their production of antifungal molecules and their role in biological control of plant disease. Burkholderia cepacia also produces antifungal activities, but its biological control activity is much less well characterized, in part due to difficulties in applying genetic tools. Here we report genetic and biochemical characterization of a soil isolate of B. cepacia relating to its production of an unusual antibiotic that is very active against a variety of soil fungi. Purification and preliminary structural analyses suggest that this antibiotic (called AFC-BC11) is a novel lipopeptide associated largely with the cell membrane. Analysis of conditions for optimal production of AFC-BC11 indicated stringent environmental regulation of its synthesis. Furthermore, we show that production of AFC-BC11 is largely responsible for the ability of B. cepacia BC11 to effectively control the damping-off of cotton caused by the fungal pathogen Rhizoctonia solani in a gnotobiotic system. Using Tn5 mutagenesis, we identified, cloned, and characterized a region of the genome of strain BC11 that is required for production of this antifungal metabolite. DNA sequence analysis suggested that this region encodes proteins directly involved in the production of a nonribosomally synthesized lipopeptide. PMID:9758823

A rapid subtraction hybridization approach was used to isolate genes differentially expressed during mycelial contact between Trichoderma harzianum (Hypocrea lixii) and Rhizoctonia solani, and could serve as marker genes for selection of superior biocontrol strains. Putatively positive clones were evaluated by transcription analysis during mycelial contact with R. solani versus growth on glucose, and for their differential transcription between two strains with either strong or poor biocontrol capability before, at, and after contact with R. solani. Besides four clones, which had similarity to putative but as yet uncharacterized proteins, they comprised ribosomal proteins, proteins involved in transcriptional switch and regulation, amino acid and energy catabolism, multidrug resistance, and degradation of proteins and glucans. Transcription of three clones was evaluated in five T. harzianum strains under confrontation conditions with R. solani. Two clones-acetyl-xylane esterase AXE1 and endoglucanase Cel61b-showed significant upregulation during in vivo confrontation of a T. harzianum strain that successively demonstrated a very high antagonistic capability towards R. solani, while expression was progressively lower in a series of T. harzianum strains with intermediate to poor antagonistic activity. These clones are promising candidates for use as markers in the screening of improved T. harzianum biocontrol strains. PMID:19116716

The present study was carried out to evaluate the ability of Trichoderma harzianum (ALL 42-isolated from Brazilian Cerrado soil) to promote common bean growth and to modulate its metabolism and defense response in the presence or absence of the phytopathogenic fungi Rhizoctonia solani and Fusarium solani using a proteomic approach. T. harzianum was able to promote common bean plants growth as shown by the increase in root/foliar areas and by size in comparison to plants grown in its absence. The interaction was shown to modulate the expression of defense-related genes (Glu1, pod3 and lox1) in roots of P. vulgaris. Proteomic maps constructed using roots and leaves of plants challenged or unchallenged by T. harzianum and phytopathogenic fungi showed differences. Reference gels presented differences in spot distribution (absence/presence) and relative volumes of common spots (up or down-regulation). Differential spots were identified by peptide fingerprinting MALDI-TOF mass spectrometry. A total of 48 identified spots (19 for leaves and 29 for roots) were grouped into protein functional classes. For leaves, 33%, 22% and 11% of the identified proteins were categorized as pertaining to the groups: metabolism, defense response and oxidative stress response, respectively. For roots, 17.2%, 24.1% and 10.3% of the identified proteins were categorized as pertaining to the groups: metabolism, defense response and oxidative stress response, respectively. PMID:24878929

We have previously demonstrated immunostimulatory activity of a fungal lectin, Rhizoctonia bataticola lectin (RBL), towards normal human peripheral blood mononuclear cells. The present study aimed to explore the anticancer activities of RBL using human leukemic T-cell lines, Molt-4, Jurkat and HuT-78. RBL exhibited significant binding (>90%) to the cell membrane that was effectively inhibited by complex glycoproteins such as mucin (97% inhibition) and asialofetuin (94% inhibition) but not simple sugars such as N-acetyl-D-galactosamine, glucose and sucrose. RBL induced a dose and time dependent inhibition of proliferation and induced cytotoxicity in the cell lines. The percentage of apoptotic cells, as determined by hypodiploidy, was 33% and 42% in Molt-4 and Jurkat cells, respectively, compared to 3.11% and 2.92% in controls. This effect was associated with a concomitant decrease in the G0/G1 population. Though initiator caspase-8 and -9 were activated upon exposure to RBL, inhibition of caspase-8 but not caspase-9 rescued cells from RBL-induced apoptosis. Mechanistic studies revealed that RBL induced cleavage of Bid, loss of mitochondrial membrane potential and activation of caspase-3. The expression of the anti-apoptotic proteins Bcl-2 and Bcl-X was down regulated without altering the expression of pro-apoptotic proteins- Bad and Bax. In contrast to leukemic cells, RBL did not induce apoptosis in normal PBMC, isolated CD3+ve cells and undifferentiated CD34+ve hematopoietic stem and progenitor cells (HSPCs). The findings highlight the differential effects of RBL on transformed and normal hematopoietic cells and suggest that RBL may be explored for therapeutic applications in leukemia. PMID:24244478

The metabolic control of plant growth regulator production by the plant pathogenic fungus Rhizoctonia solani Kühn (teleomorph=Thanatephorus cucumeris (A.B. Frank) Donk) and consequences associated with the parasitic and saprobic activity of the fungus were investigated. Fourteen genetically distinct isolates of the fungus belonging to anastomosis groups (AG) AG-3, AG-4, and AG-1-IA were grown on Vogel's minimal medium N with and without the addition of a 25 mM quinic acid (QA) source of carbon. The effect of QA on fungal biomass was determined by measuring the dry wt of mycelia produced under each growth condition. QA stimulated growth of 13 of 14 isolates of R. solani examined. The production of phenylacetic acid (PAA) and the chemically related derivatives 2-hydroxy-PAA, 3-hydroxy-PAA, 4-hydroxy-PAA, and 3-methoxy-PAA on the two different media was compared by gas chromatography coupled with mass spectrometry (GC-MS). The presence of QA in the growth medium of R. solani altered the PAA production profile, limiting the conversion of PAA to derivative forms. The effect of QA on the ability of R. solani to cause disease was examined by inoculating tomato (Solanum lycopersicum L.) plants with 11 isolates of R. solani AG-3 grown on media with and without the addition of 25 mM QA. Mean percent survival of tomato plants inoculated with R. solani was significantly higher when the fungal inoculum was generated on growth medium containing QA. The results of this study support the hypotheses that utilization of QA by R. solani leads to reduced production of the plant growth regulators belonging to the PAA metabolic complex which can suppress plant disease development. PMID:23380633

DNA polymorphism in the 18S nuclear rRNA gene region was investigated by using 11 restriction endonucleases for 161 isolates of 25 intraspecific groups (ISGs) representing 11 reported anastomosis groups (AGs) of Rhizoctonia solani. A PCR-based restriction mapping method in which enzymatically amplified DNA fragments and subfragments were digested with one or two restriction enzymes was employed. Four types of DNA restriction maps of this region were constructed for these 25 ISGs. Map type I of the 18S rDNA region was represented by isolates of a majority of R. solani ISGs. Map types II and III, represented by ISG 2E and 9 isolates and 5C isolates, respectively, differed from map I by the absence of one (map type II) or two (map type III) restriction sites. Map type IV, represented by ISG 10A and B (or AG 10) isolates, showed significant restriction site variations, with five enzymes in this region compared with those of the remaining ISGs or AGs. Ten of the 25 restriction sites in the 18S rRNA gene region were informative and selected for analysis. Previously reported restriction maps of the 5.8S rRNA gene region, including the internal transcribed spacers, were aligned with each other, and 12 informative restriction sites were identified. These data were used alone and in combination to evaluate group relationships. Analyses derived from these data sets by maximum parsimony and likelihood methods showed that AG 10 isolates were distinct and distantly related to the majority isolates of the other AGs of this species complex. PMID:7618879

Sharp eyespot disease (primarily caused by the pathogen Rhizoctonia cerealis) and freezing stress are important yield limitations for the production of wheat (Triticum aestivum). Here, we report new insights into the function and underlying mechanisms of an ethylene response factor (ERF) in wheat, Pathogen-Induced ERF1 (TaPIE1), in host responses to R. cerealis and freezing stresses. TaPIE1-overexpressing transgenic wheat exhibited significantly enhanced resistance to both R. cerealis and freezing stresses, whereas TaPIE1-underexpressing wheat plants were more susceptible to both stresses relative to control plants. Following both stress treatments, electrolyte leakage and hydrogen peroxide content were significantly reduced, and both proline and soluble sugar contents were elevated in TaPIE1-overexpressing wheat, whereas these physiological traits in TaPIE1-underexpressing wheat exhibited the opposite trend. Microarray and quantitative reverse transcription-polymerase chain reaction analyses of TaPIE1-overexpressing and -underexpressing wheat plants indicated that TaPIE1 activated a subset of defense- and stress-related genes. Assays of DNA binding by electrophoretic mobility shift and transient expression in tobacco (Nicotiana tabacum) showed that the GCC boxes in the promoters of TaPIE1-activated genes were essential for transactivation by TaPIE1. The transactivation activity of TaPIE1 and the expression of TaPIE1-activated defense- and stress-related genes were significantly elevated following R. cerealis, freezing, and exogenous ethylene treatments. TaPIE1-mediated responses to R. cerealis and freezing were positively modulated by ethylene biosynthesis. These data suggest that TaPIE1 positively regulates the defense responses to R. cerealis and freezing stresses by activating defense- and stress-related genes downstream of the ethylene signaling pathway and by modulating related physiological traits in wheat. PMID:24424323

One of the most important environmental factors that regulate the growth and antagonistic efficacy of biocontrol agents is the medium. The aim of this paper was to find the nitrogen and carbon sources that provide maximum biomass production of strains P-5 and P-6 (Pseudomonas fluorescens), B-3 and B-16 (Bacillus subtilis) and minimum cost of media, whilst maintaining biocontrol efficacy. All of the strains were grown in seven liquid media (pH=6.9) including: sucrose + yeast extract, molasses of sugar beet + yeast extract in 2:1 and 1:1 w/w ratios, molasses of sugar beet + urea, nutrient broth, molasses and malt extract, at an initial inoculation of 1 x 10(5) CFU ml(-1). Cells from over night cultures used to inoculate soil at 1 x 10(9) CFU cm(-3) soil. At the same time, fungal inoculum (infected millet seed with Rhizoctonia solani) was added to soil at the rate of 2 g kg(-1) soil. Results indicated that growth of P-6, B-3 and B-16 in molasses + yeast extract (1:1 w/w) medium was significantly higher than in the other media. Molasses + yeast extract (1:1 and 2:1 w/w) media supported rapid growth and high cell yields in P-5. In greenhouse condition, results indicated that the influence of the media on the biocontrol efficacy of P-5, P-6, B-3 and B-16 was the same and Pseudomonas fluorescens P-5 in molasses and malt extract media reduced the severity of disease up to 72.8 percent. On the other hand, there were observed significant differences on bean growth after one month in greenhouse. P-5 in molasses + yeast extract (1:1 w/w) medium had the most effects on bean growth promotion. In this study molasses media showed good yield efficacy in all of the strains. The high sucrose concentration in molasses justifies the high biomass in all of the strains. Also, the low cost of molasses allows its concentration to be increased in media. On the other hand, yeast extract was the best organic nitrogen source for antagonist bacteria but it is expensive for an industrial process. So it should be replaced by another industrial product instead of yeast extract, which confirm by an economic and technological study. The results obtained in this study could be used to provide a reliable basis to increase the population of biocontrol agents in fermentation process. PMID:18396833

Background The soil fungus Rhizoctonia solani anastomosis group 3 (AG-3) is an important pathogen of cultivated plants in the family Solanaceae. Isolates of R. solani AG-3 are taxonomically related based on the composition of cellular fatty acids, phylogenetic analysis of nuclear ribosomal DNA (rDNA) and beta-tubulin gene sequences, and somatic hyphal interactions. Despite the close genetic relationship among isolates of R. solani AG-3, field populations from potato and tobacco exhibit comparative differences in their disease biology, dispersal ecology, host specialization, genetic diversity and population structure. However, little information is available on how field populations of R. solani AG-3 on potato and tobacco are shaped by population genetic processes. In this study, two field populations of R. solani AG-3 from potato in North Carolina (NC) and the Northern USA; and two field populations from tobacco in NC and Southern Brazil were examined using sequence analysis of two cloned regions of nuclear DNA (pP42F and pP89). Results Populations of R. solani AG-3 from potato were genetically diverse with a high frequency of heterozygosity, while limited or no genetic diversity was observed within the highly homozygous tobacco populations from NC and Brazil. Except for one isolate (TBR24), all NC and Brazilian isolates from tobacco shared the same alleles. No alleles were shared between potato and tobacco populations of R. solani AG-3, indicating no gene flow between them. To infer historical events that influenced current geographical patterns observed for populations of R. solani AG-3 from potato, we performed an analysis of molecular variance (AMOVA) and a nested clade analysis (NCA). Population differentiation was detected for locus pP89 (?ST = 0.257, significant at P < 0.05) but not for locus pP42F (?ST = 0.034, not significant). Results based on NCA of the pP89 locus suggest that historical restricted gene flow is a plausible explanation for the geographical association of clades. Coalescent-based simulations of genealogical relationships between populations of R. solani AG-3 from potato and tobacco were used to estimate the amount and directionality of historical migration patterns in time, and the ages of mutations of populations. Low rates of historical movement of genes were observed between the potato and tobacco populations of R. solani AG-3. Conclusion The two sisters populations of the basidiomycete fungus R. solani AG-3 from potato and tobacco represent two genetically distinct and historically divergent lineages that have probably evolved within the range of their particular related Solanaceae hosts as sympatric species. PMID:17854492

Sharp eyespot disease (primarily caused by the pathogen Rhizoctonia cerealis) and freezing stress are important yield limitations for the production of wheat (Triticum aestivum). Here, we report new insights into the function and underlying mechanisms of an ethylene response factor (ERF) in wheat, Pathogen-Induced ERF1 (TaPIE1), in host responses to R. cerealis and freezing stresses. TaPIE1-overexpressing transgenic wheat exhibited significantly enhanced resistance to both R. cerealis and freezing stresses, whereas TaPIE1-underexpressing wheat plants were more susceptible to both stresses relative to control plants. Following both stress treatments, electrolyte leakage and hydrogen peroxide content were significantly reduced, and both proline and soluble sugar contents were elevated in TaPIE1-overexpressing wheat, whereas these physiological traits in TaPIE1-underexpressing wheat exhibited the opposite trend. Microarray and quantitative reverse transcription-polymerase chain reaction analyses of TaPIE1-overexpressing and -underexpressing wheat plants indicated that TaPIE1 activated a subset of defense- and stress-related genes. Assays of DNA binding by electrophoretic mobility shift and transient expression in tobacco (Nicotiana tabacum) showed that the GCC boxes in the promoters of TaPIE1-activated genes were essential for transactivation by TaPIE1. The transactivation activity of TaPIE1 and the expression of TaPIE1-activated defense- and stress-related genes were significantly elevated following R. cerealis, freezing, and exogenous ethylene treatments. TaPIE1-mediated responses to R. cerealis and freezing were positively modulated by ethylene biosynthesis. These data suggest that TaPIE1 positively regulates the defense responses to R. cerealis and freezing stresses by activating defense- and stress-related genes downstream of the ethylene signaling pathway and by modulating related physiological traits in wheat. PMID:24424323

Gliocladium roseum was found to be the most common and probably the most effective mycoparasite in potato fields in the northern parts of the Netherlands. It is able to parasitize and kill living hyphae at temperatures of 12°C and higher. Sclerotia ofR. solani are often infected and killed by this fungus under suitable conditions, i.e. at temperatures of 16°C and

, stunting, inhibited rooting, and malformed plants when fungicides are used on bedding plants (7, 11, 21, 31). Bolton (7) found that PCNB caused definite stunting in impatiens, damaged petunia, and injured tomato seedlings when used as a drench. Benomyl..., stunting, inhibited rooting, and malformed plants when fungicides are used on bedding plants (7, 11, 21, 31). Bolton (7) found that PCNB caused definite stunting in impatiens, damaged petunia, and injured tomato seedlings when used as a drench. Benomyl...

Approximately 50 single-basidiospore isolates (SBIs) obtained from each of 16 field isolates of Thanatephorus cucumeris AG-1 IC were examined for heterokaryon formation. All SBIs obtained from each field isolate were divided into two mating groups (SBIs-M1 and SBIs-M2), and tufts of mycelia were formed in the contact zone between colonies of paired SBIs-M1 and -M2 based on 0.5 % charcoal agar medium. Tufts were produced from all possible pairing between SBIs from non-parental field isolates. Hyphal anastomosis reactions indicated no cell death and random cell death at the contact cell, and was not related to tuft formation. AFLP phenotypes of SBIs from each field isolate were not identical to each other and were different from their parental field isolate. AFLP phenotypes of the tuft isolates formed from SBIs-M1 and SBIs-M2 from each field isolate were heterokaryotic. Moreover, several SBIs also formed tufts with their parental and non-parental field isolates. AFLP phenotypes of these tuft isolates suggested that they were all heterokaryotic. Results of these experiments suggest that T. cucumeris AG-1 IC is heterothallic and bipolar, and that genetic exchange can occur between homokaryotic and heterokaryotic isolates (Buller phenomenon). PMID:18692371

, was naturally infested with P. ultimum #12;(100 colony-forming units/cm3 soil). This site also had low levels conditions were warm and dry after planting, so plots were irrigated to saturation 3 days after planting

Under conditions of sulfur (S)-deficient soil, applied S fertilization had a significant repressive effect on fungal infections such as that of oilseed rape and grapes with light leaf spot (Pyrenopeziza brassicae) and powdery mildew (Uncinula necator), respectively. For potatoes (Solanum tuberosum L.) it has been shown in earlier literature that elemental sulfur fertilization increased yield of potato tubers and improved

The role of extracellular chitinase in the biocontrol activity of Trichoderma virens was examined using genetically manipulated strains of this fungus. The T. virens strains in which the chitinase gene (cht42) was disrupted (KO) or constitutively over-expressed (COE) were constructed through genetic transformation. The resulting\\u000a transformants were stable and showed patterns similar to the wild-type (WT) strain with respect to

A microcosm incubation study using an aquic brown soil from northeast China (a Cambisol in the UN Food and Agriculture Organization FAO Soil Taxonomy) was conducted to examine the effects of different concentrations (0, 50, 150, and 250 mg kg) of methamidophos (O,S-dimethyl phosphoramidothioato) on Pseudomonas, one of the most important gram-negative bacteria in soil. Amplified ribosomal DNA restriction analysis

to Parmeter et al (26), characteristics used to delin- R. 1 f ** (t) h p f f ~Th h i (Frank) Donk; (ii) multinucleate cells in young vegetative hyphae; (iii) prominent septal pore apparatus; (iv) branching near the distal septum of cells in young hyphae...; (v) constriction of the branch and formation of a septum in the branch near the point of origin; and (vi) some shade of brown. Characteristics usually present, which may be lacking in individual i. solates, are (vii) monilioid cells; (vi. ii...

During the 1988 summer-fall growing cycle in the Mexican region of Leon, Guanajuato the fungicide 2-(Thiocyanomethylthio) benzothiazole (TCMTB) was evaluated applying it at the rate of 6, 8 and 10 liters per hectare for the control of soil borne Black Scurf R. solani. A randomized block design with four reps was used. An evaluation was made of the following: emerged

Biofumigation is increasingly viewed as a potentially useful technique for controlling soil-borne crop pathogens, but its efficacy has not systematically been demonstrated at field scale. We investigated the differences in efficacy observed in the field, by analysing the mechanisms by which a Brassica cover crop can act as a biofumigant crop in the prevention of soil-borne disease development. We hypothesised

shown to be unimportant in R. solani resistance. Two rounds of recurrent phenotypic selection were effective in increasing the resistance of selected HT lines to R. solani. One cycle of phenotypic selection for P. aphanidermatum resistance was found...

from Tocantins, one from Maranha~ o, and one from Cuba occupied the tips of the network, indicating, PiauiÂ´, Tocantins, ParaÂ´ , and Roraima States (Meyer and Yorinori, 1999). Historically, the first w

Potassium and chloride both suppressed Rhizoctonia blight in St. Augustinegrass and the two combined together as KCl was superior to K or Cl applied separately. Potassium applied as K?SO? showed little disease suppression. Increasing rates of KCl...

...on corn for efficacy against seedling infections of soilborne plant pathogenic fungi Fusarium, Rhizoctonia, Pythium and Colletotrichum, and to aid in suppression of late season stalk rot. This is a crop-destruct EUP. Amount of product to be used:...

A series of fungal laccases (Polyporus pinsitus, Rhizoctonia solani, Myceliophthora hermophila, Scytalidium thermophilum) and one bilirubin oxidase (Myrothecium verrucaria) have been studied to determine their redox potential, specificity, and stability. Polyporus and Rhizoctonia laccases possess potentials near 0.7–0.8 V (vs. NHE), while other oxidases have potentials near 0.5 V. It is observed that higher redox potential correlates with higher activity.

) the proteins are active in vitro at microcellular level against wide range of fungi including human and plant pathogens including Rhizoctonia solani, C. albicans and Aspergillus fumigatus. Induction of ?-glucanase in sorghum has been reported in response...) the proteins are active in vitro at microcellular level against wide range of fungi including human and plant pathogens including Rhizoctonia solani, C. albicans and Aspergillus fumigatus. Induction of ?-glucanase in sorghum has been reported in response...

) the proteins are active in vitro at microcellular level against wide range of fungi including human and plant pathogens including Rhizoctonia solani, C. albicans and Aspergillus fumigatus. Induction of ?-glucanase in sorghum has been reported in response...) the proteins are active in vitro at microcellular level against wide range of fungi including human and plant pathogens including Rhizoctonia solani, C. albicans and Aspergillus fumigatus. Induction of ?-glucanase in sorghum has been reported in response...

A novel slightly distorted octahedral complex of Cr(III) of norfloxacin (Nor) with the formula [CrIII(Nor)(Bipy)Cl2]Cl·2CH3OH has been synthesized hydrothermally in the presence of a N-containing heterocyclic compound 2,2?-bipyridyl (Bipy). The complex was characterized with FT-IR, elemental analysis, UV-visible spectroscopy, and X-ray crystallography. Spectral studies suggest that the Nor acts as a deprotonated bidentate ligand. Thermal studies were also carried out. The synthesised complex was screened against four fungi Pythium aphanidermatum (PA), Sclerotinia rolfsii (SR), Rhizoctonia solani (RS), and Rhizoctonia bataticola (RB).

Aqueous extracts from seeds of four woodland ground flora species (Hyacinthoides non-scripta, Allium ursinum, Digitalis purpurea and Hypericum pulchrum) were tested for antifungal activity using a petriplate technique. Four species of fungi were investigated. The growth of three of these (Trichoderma viride, Rhizoctonia solani and Pythium sp.) was not affected by any of the seed coat extracts. The growth of

...subtilis strain GB03 is used to prevent, control and suppress plant disease on barley...to prevent or reduce several types of fungal and bacterial pests on artichoke, asparagus...increasing yields and suppressing soil-borne fungal diseases such as Rhizoctonia and...

...subtilis strain GB03 is used to prevent, control and suppress plant disease on barley...to prevent or reduce several types of fungal and bacterial pests on artichoke, asparagus...increasing yields and suppressing soil-borne fungal diseases such as Rhizoctonia and...

Two Pseudomonas fluorescens strains viz., PF1 and FP7 which inhibited the mycelial growth of sheath blight fungus Rhizoctonia solani and increased the seedling vigour of rice plants in vitro were selected for assessing induced systemic resistance (ISR) against R. solani in rice. The Pseudomonas application as a bacterial suspension or a talc-based formulation through seed, root, soil and foliar application

In this study, inhibitory activities of leaf essential oils from Cinnamomum osmophloeum and Cinnamomum zeylanicum and their major constituents (trans-cinnamaldehyde and eugenol) against Rhizoctonia solani were investigated. Furthermore, the relationship between the antipathogenic activity and the chemical structure of trans-cinnamaldehyde and eugenol is discussed. Results demonstrated that leaf essential oils and their major constituents from C. osmophloeum and C. zeylanicum

Seventy-five percent of the peanuts (Arachus hypogaia) produced in the United States are grown in the Atlantic Coastal Plain region. Portions of this area, including Alabama and Georgia, exhibit a subtropical climate that promotes soil-borne plant fungal diseases. Most fields receive repeated fungicide applications during the growing season to suppress the disease causing organisms, such as Sclerotium rolfsii, Rhizoctonia solani,

This article was originally published in the Encyclopedia of Virology, Volumes 1Â­5 published, Ochoa W F, Baker T S and Nibert M L. Partitiviruses: General Features. Encyclopedia of Virology, 5 vols of the genome of a partitivirus from the basidiomycete Rhizoctonia solani. Journal of General Virology 81: 549

In this study, the in vitro potential of 42 Trichoderma spp. were evaluated against four isolates of soil borne phytopathogenic fungi viz., Rhizoctonia solani, Macrophomina sp., Sclerotium rolfsii and Pythium aphanidermatum in dual culture techniques and through production of volatile and non-volatile inhibitors. In vitro screening results showed that the proportion of isolates with antagonistic activities was highest for the

The aim of the study is to investigate the biocontrol mechanisms of Trichothecium roseum MML003 against the rice sheath blight (ShB) pathogen, Rhizoctonia solani as the former exhibited strong antagonistic activity against the latter. It has been found that T. roseum MML003 did not show any hyperparasitic interaction against R. solani. Further, it did not produce siderophores and hydrogen cyanide.

Introduction Proper irrigation timing can maximize sugar- beet yields while minimizing disease- cially with furrow irrigation. Root diseases such as rhizomania and rhizoctonia root and crown rots will be reduced. Unnecessary irrigations can be reduced if grow- ers use information on water status at deeper

An investigation was undertaken to evaluate a set of cyanobacterial strains in terms of production of biocidal compounds exhibiting\\u000a allelochemical and fungicidal properties. Two cyanobacterial strains — Anabaena sp. and Calothrix sp. were selected for further investigation, on the basis of their larger inhibition zones on the lawn of Synechocystis and Synechococcus sp. and two phytopathogenic fungi — Rhizoctonia bataticola

The economic importance and current progress made in studies of the host-parasite relationship and identification of sources of resistance and breeding strategies of some important biotic diseases of pea are reviewed in this paper. The root rot complex caused by Rhizoctonia solani, Fusarium solani, Aphanomyces euteiches, Pythium ultimum and Fusarium oxysporum f. sp. pisi, race 1 and 2 has been

zone have been found to inter- fere with calcium uptake and to increase the inci- dence of pod rotting organisms such as Pythium and Rhizoctonia. If you have any questions about soil testing, consult your county Extension agent- agriculture. Calcium..., this disease is much easier to control. These fungicides also aid in the control of several less important soil diseases. Fields that sometimes receive excess moisture may develop a type of Pythium pod rot that responds to the fungicide Ridomil ? . Sclerotinia...

Rhizoctonia solani and Fusarium solani were isolated from diseased lentil roots showing damping-off and root rot collected from different locations of New Valley governorate. R. solani isolate R-1 and F. solani isolate FS-9 were the highest virulent isolates. The influence of some agricultural factors on severity of damping-off and root rot disease was studied under greenhouse and field conditions. Intercropping cumin, anise,

An anti-fungal protein GAFP-1 (Gastrodia anti-fungal protein, also called gastrodianin) was purified from Gastrodia elata B1. f. flavida S. Chow (Orchidaceae), a parasitic plant on the fungus Armillaria mellea. It can inhibit the hyphal growth of some phytopathogenic fungi such as Valsa ambiens, Rhizoctonia solani, Gibberella zeae, Ganoderma lucidum and Botrytis cinerea in vitro. GAFP-1 is a monomer with a

, or biocontrol, is the use of a living organism to control another pathogenic organism (Vinale et al., 2008). In this case, Trichoderma species can directly parasitize fungal plant pathogens such as Pythium ultimum and Rhizoctonia solani (Jayaraj... attention (Mercado-Blanco & Bakker, 2007). However, the roles and interactions of siderophores in fungal biocontrol agents have yet to be explored. T. virens is a plant symbiotic, avirulent fungus whose capabilities for biological control have been...

Four rhizobacterial strains and acibenzolar-S-methyl (ASM), a chemical activator, which suppressed foliar blight of amaranthus (Amaranthus tricolor L.) caused by Rhizoctonia solani K?hn were evaluated for their effect on plant growth. The experiments were performed both under sterile and non-sterile soil\\u000a conditions, in the presence or absence of the pathogen. In all cases, plants treated with ASM showed significant reduction

Influence of laboratory growth conditions and soil conditions on the survival of Pseudomonas fluorescens R1, a spontaneous rifamycin-resistant mutant of P. fluorescens W1, in soil was investigated. Strain R1 is antagonistic to Gaeumannomyces graminis and Rhizoctonia solani in vitro. Characteristics of W1 are scarcely different from those of R1 with respect to growth rates, plasmids, and the ability to use

The aim of the present work was to study the effects of vesicular-arbuscular mycorrhiza (VAM) and Trichoderma virdi (T. virdi) fungi as deterrents against Rhizoctonia solani (R. solani) and Fusarium solani (F. solani) infections on the growth and quality of sugar beet. Two experiments were carried out in the greenhouse at the Agriculture\\u000a Research Center, Giza, Egypt, under greenhouse conditions.

Forty-seven isolates representing all biovars of Pseudomonas fluorescens (biovars I to VI) were collected from the rhizosphere of field-grown sugar beet plants to select candidate strains for biological control of preemer- gence damping-off disease. The isolates were tested for in vitro antagonism toward the plant-pathogenic microfungi Pythium ultimum and Rhizoctonia solani in three different plate test media. Mechanisms of fungal

This study investigated the interactions between the arbuscular mycorrhizal fungus (AMF) Glomus mosseae and the plant growth-promoting fungi (PGPF) Penicillium simplicissimum GP17-2 and Trichoderma harzianum GT3-2 in relation to their colonization of roots and the rhizosphere of cucumber (Cucumis sativus L.), and their effect on plant growth and suppression of the damping-off pathogen Rhizoctonia solani. Combined inoculation of T. harzianum

Summary The viability of five pathogens was decreased by treatment with hot water when tested in vitro.Polyscytalum pustulans was most sensitive andRhizoctonia solani least sensitive.\\u000a \\u000a Potato tubers were exposed to 55C for 5 min in a commercial continuous hot water treatment plant using naturally contaminated\\u000a seed tubers and tubers which had been inoculated by dipping in comminuted cultures. The frequency of

Laccases from the fungiRhizoctonia praticola andTrametes versicolor as well as horseradish peroxidase and tyrosinase were evaluated for their ability to polymerize phenolic contaminants. The removal of phenols through polymerization depended on the chemical structure and concentration of the substrate, pH of the reaction mixture, activity of the enzyme, length of incubation, and temperature. The enzymes retained their activity throughout a

The aim of two year investigation was the valuation the effect of biopreparate Polyversum (B.A.S. Pythium oligandrum) and preparate Biochikol 020 PC (B.A.S. chitosan) used in control of potato against Phytophthora blight on the tuber infestation during storage by Helminthosporium solani and tuber infestation by sclerotia of Rhizoctonia solani. As the standard fungicide Vitavax 200 FS (B.A.S. karboxin and thiuram) was used. After harvesting 100 tubers from each plots was collected and put in storage. The analysis of tuber infestation by Rhizoctonia solani and Helminthosporium solani was made after harvesting (September) and later every 3 months during storage period (December, March). The percent of diseased tubers in tested sample and also infestation degree of bulbs using 5-degree scale was estimated. The received results of investigations ascertained, that all tested preparations during potato vegetation influenced on lower (in comparison with control) degree of bulbs infestation by sclerots of Rhizoctonia solani and the mean degree of infestation by Helminthosporium solani. Moreover the percent of diseased tubers infected by pathogens with tested preparations combination was significant lower than in control. PMID:18396836

The genus Cymbopogon that belongs to the Poaceae (Graminae) has some important aromatic species whit remarkable commercial value. Essential oils from different species of the Cymbopogon are used in the perfumery, cosmetic and soap industries and some of them have antifungal and insecticide activity. In this study, antifungal activity of C. parkeri essential oil on the growth of Rhizoctonia solani, Pyricularia orizea and Fusarium oxysporum, three important phytopathogenic fungi, was investigated. The essential oil was extracted from the air-dried parts in flowering stage by hydrodistillation in a Clevenger type apparatus, and Growth inhibition of Rhizoctonia solani, Pyricularia orizea, Fusarium oxysporum for 15, 30, 75,150, 300 and 600 microl L(-1) dosage of the essential oil in PDA was examined in vitro by media mixed method and was compared with control. Antifungal activity was determined in terms of growth inhibitory concentration for 50% growth inhibitory (EC50 microI L(-1)) and inhibition percentage of some dosages was obtained. The results showed that concentration of 600 microl L(-1) of the essential oil completely inhibits the growth of all tested fungi. EC50 for Rhizoctonia solani, Pyricularia orizea, Fusarium oxysporum were counted 39.82, 72.00 and 43.63 microl L(-1) respectively. The results indicated that the essential oil has strong fungi state activity. PMID:17390842

Pseudomonas fluorescens HC1-07, previously isolated from the phyllosphere of wheat grown in Hebei province, China, suppresses the soilborne disease of wheat take-all, caused by Gaeumannomyces graminis var. tritici. We report here that strain HC1-07 also suppresses Rhizoctonia root rot of wheat caused by Rhizoctonia solani AG-8. Strain HC1-07 produced a cyclic lipopeptide (CLP) with a molecular weight of 1,126.42 based on analysis by electrospray ionization mass spectrometry. Extracted CLP inhibited the growth of G. graminis var. tritici and R. solani in vitro. To determine the role of this CLP in biological control, plasposon mutagenesis was used to generate two nonproducing mutants, HC1-07viscB and HC1-07prtR2. Analysis of regions flanking plasposon insertions in HC1-07prtR2 and HC1-07viscB revealed that the inactivated genes were similar to prtR and viscB, respectively, of the well-described biocontrol strain P. fluorescens SBW25 that produces the CLP viscosin. Both genes in HC1-07 were required for the production of the viscosin-like CLP. The two mutants were less inhibitory to G. graminis var. tritici and R. solani in vitro and reduced in ability to suppress take-all. HC1-07viscB but not HC-07prtR2 was reduced in ability to suppress Rhizoctonia root rot. In addition to CLP production, prtR also played a role in protease production. PMID:24512115

Three acyl derivatives of chitosan (CS) with different side chains were synthesized and their structures were characterized. Their swelling behavior was investigated. The antifungal behavior of these chitosan derivatives was investigated in vitro on the mycelial growth, sporulation and germination of conidia or sclerotia of the sugar-beet pathogens, Rhizoctonia solani K"uhn (AG2-2) and Sclerotium rolfsii Sacc. All the prepared derivatives had a significant inhibiting effect on the different stages of development on the germination of conidia or sclerotia of all the investigated fungi. In the absence of chitosan and its derivative, R. solani exhibited the fastest growth of the fungi studied. PMID:25002014

for different disease-causing organisms. Sclerotia of Rhizoctonia solani (the fungus that causes sheath blight) survive an average of 12 to 18 months in the soil. Kernel smut fungus spores (Neouossia horrida) can remain alive more than 10 years. As a result... chart (table 1) for specific recommendations. SOUTHERN BLIGHT (fungus - Sclerotium ro lIs ii) Southern blight can attack rice in the one- to three leaf stage and may kill large numbers of plants when weather is warm and moist. A white cottony mold...

Phytophthora tropicalis was isolated from Hedera helix and Epipremnum aureum showing discoloration of leaves, necrosis of shoot base, spread upwards and on roots. The species was detected from 7/8 plants of Hedera and 3/4 of Epipremnum. Additionally Botrytis cinerea, Fusarium avenaceum and Rhizoctonia solani were recovered from some of diseased plants. P. tropicalis caused leaf necrosis of 13 plant species and tomato seedlings. The quickest spread of necrosis was observed on leaves of Peperomia magnoliaefolia, Pelargonium zonale and Phalaenopsis x hybridum. The disease developed at temperature ranged from 10 degrees to 32.5 degrees C with optimum 30 degrees C. PMID:17390874

This selection of online fact sheets concerned with plant diseases was compiled by Professor Gary W. Moorman, a Professor of Plant Pathology at Penn State. The concise fact sheets address "common diseases of plants frequently grown in greenhouses, interiorscapes, and in outdoor landscapes and nurseries in the northeastern U.S." The sheets are organized under categories for Woody Ornamental, and Floral and Foliage Plants, as well as a General Information category. Factsheets address such diseases as Bacterial Leaf Scorch, Pythium Root Rot, Botrytis Blight, Rhizoctonia, and more. There are sheets for a wide variety of plants and trees including Iris, Tulip, Maple, and Oak, to name a few.

We isolated Rhizoctonia-like fungi from populations of the threatened orchid Cypripedium macranthos. In ultrastructural observations of the septa, the isolates had a flattened imperforate parenthesome consisting of two electron-dense membranes bordered by an internal electron-lucent zone, identical to the septal ultrastructure of Rhizoctonia repens (teleomorph Tulasnella), a mycorrhizal fungus of many orchid species. However, hyphae of the isolates did not fuse with those of known tester strains of R. repens and grew less than half as fast as those of R. repens. In phylogenetic analyses, sequences for rDNA and internal transcribed spacer (ITS) regions of the isolates were distinct from those of the taxonomically identified species of Tulasnella. On the basis of the ITS sequences, the isolates clustered into two groups that corresponded exactly with the clades demonstrated for other Cypripedium spp. from Eurasia and North America despite the geographical separation, suggesting high specificity in the Cypripedium-fungus association. In addition, the two phylogenetic groups corresponded to two different plant clones at different developmental stages. The fungi from one clone constituted one group and did not belong to the other fungal group isolated from the other clone. The possibility of switching to a new mycorrhizal partner during the orchid's lifetime is discussed. PMID:19449040

The hitherto unknown relationships between the European orchid Spiranthes spiralis (L.) Chevall and its internally associated fungi were explored by a combined approach involving microscopy-based investigations at a morpho-histological level as well as by molecular analyses of the identity of the eukaryotic endophytes present in the root tissue of the plant. We found that this orchid which is currently reported to have a vulnerable status in northern Italy, can host and interact with at least nine types of fungi. Some of these fungi show similarity to mycorrhizal genera found in orchids such as the Ceratobasidium-Rhizoctonia group. Other fungi found are from the genera Davidiella (Ascomycota), Leptosphaeria (Ascomycota), Alternaria (Ascomycota), and Malassezia (Basidiomycota), some of which until have not previously been reported to have an endophytic relationship with plants. The repeated occurrence of often pathogenic fungi such as Fusarium oxysporum, Bionectria ochroleuca, and Alternaria sp., within healthy specimens of this orchid suggests a tempered interaction with species that are sometimes deleterious to non-orchid plants. The fact is reminiscent of the symbiotic compromise established by orchids with fungi of the rhizoctonia group. PMID:22483052

ABSTRACT The impact of Brassica napus seed meal on the microbial complex that incites apple replant disease was evaluated in greenhouse trials. Regardless of glucosinolate content, seed meal amendment at a rate of 0.1% (vol/vol) significantly enhanced growth of apple and suppressed apple root infection by Rhizoctonia spp. and Pratylenchus penetrans. High glucosinolate B. napus cv. Dwarf Essex seed meal amendments did not consistently suppress soil populations of Pythium spp. or apple root infection by this pathogen. Application of a low glucosinolate containing B. napus seed meal at a rate of 1.0% (vol/vol) resulted in a significant increase in recovery of Pythium spp. from apple roots, and a corresponding reduction in apple seedling root biomass. When applied at lower rates, B. napus seed meal amendments enhanced populations of fluorescent Pseudomonas spp., but these bacteria were not recovered from soils amended with seed meal at a rate of 2% (vol/vol). Seed meal amendments resulted in increased soil populations of total bacteria and actinomycetes. B. napus cv. Dwarf Essex seed meal amendments were phytotoxic to apple when applied at a rate of 2% (vol/vol), and phytotoxicity was not diminished when planting was delayed for as long as 12 weeks after application. These findings suggest that B. napus seed meal amendments can be a useful tool in the management of apple replant disease and, in the case of Rhizoctonia spp., that disease control operates through mechanisms other than production of glucosinolate hydrolysis products. PMID:18942997

ABSTRACT Systematic studies were conducted to elucidate the role of different soil microbial groups in the development of apple replant disease. Populations of targeted microorganisms were reduced by the application of semiselective biocides and soil pasteurization. Bacteria were not implicated in the disease, because application of the antibiotic chloramphenicol reduced soil populations of bacteria but failed to improve growth of apple transplants, while enhanced growth was achieved at pasteurization temperatures that did not alter attributes of the bacterial community recovered from apple roots. Populations of Pratylenchus penetrans were below the damage threshold level in eight of nine orchards surveyed, and nematicide applications failed to enhance apple growth in four of five replant soils tested, indicating that plant parasitic nematodes have a minor role or no role in disease development. Application of the fungicide difenconazole or metalaxyl enhanced growth of apple in all five replant soils, as did fludioxinil in the two soils tested. Soil pasteurization enhanced growth of apple and resulted in specific changes in the composition of the fungal community isolated from the roots of apple seedlings grown in these treated soils. Cylindrocarpon destructans, Phytophthora cactorum, Pythium spp., and Rhizoctonia solani were consistently isolated from symptomatic trees in the field and were pathogenic to apple. However, the composition of the Pythium and Rhizoctonia component and the relative contribution of any one component of this fungal complex to disease development varied among the study orchards. These findings clearly demonstrate that fungi are the dominant causal agents of apple replant disease in Washington state. PMID:18944871

The interaction of lesion nematodes, black root rot disease caused by Rhizoctonia fragariae, and root damage caused by feeding of the scarab larva, Maladera castanea, was determined in greenhouse studies. Averaged over all experiments after 12 weeks, root weight was reduced 13% by R. fragariae and 20% by M. castanea. The percentage of the root system affected by root rot was increased by inoculation with either R. fragariae (35% more disease) or P. penetrans (50% more disease) but was unaffected by M. castanea. Rhizoctonia fragariae was isolated from 9.2% of the root segments from plants not inoculated with R. fragariae. The percentage of R. fragariae-infected root segments was increased 3.6-fold by inoculation with R. fragariae on rye seeds. The presence of P. penetrans also increased R. fragariae root infection. The type of injury to root systems was important in determining whether roots were invaded by R. fragariae and increased the severity of black root rot. Pratylenchus penetrans increased R. fragariae infection and the severity of black root rot. Traumatic cutting action by Asiatic garden beetle did not increase root infection or root disease by R. fragariae. Both insects and diseases need to be managed to extend the productive life of perennial strawberry plantings. PMID:19262852

Here we present a metabolic profiling strategy employing direct infusion Orbitrap mass spectrometry (MS) and gas chromatography-mass spectrometry (GC/MS) for the monitoring of soybean's (Glycine max L.) global metabolism regulation in response to Rhizoctonia solani infection in a time-course. Key elements in the approach are the construction of a comprehensive metabolite library for soybean, which accelerates the steps of metabolite identification and biological interpretation of results, and bioinformatics tools for the visualization and analysis of its metabolome. The study of metabolic networks revealed that infection results in the mobilization of carbohydrates, disturbance of the amino acid pool, and activation of isoflavonoid, ?-linolenate, and phenylpropanoid biosynthetic pathways of the plant. Components of these pathways include phytoalexins, coumarins, flavonoids, signaling molecules, and hormones, many of which exhibit antioxidant properties and bioactivity helping the plant to counterattack the pathogen's invasion. Unraveling the biochemical mechanism operating during soybean-Rhizoctonia interaction, in addition to its significance towards the understanding of the plant's metabolism regulation under biotic stress, provides valuable insights with potential for applications in biotechnology, crop breeding, and agrochemical and food industries. PMID:25369450

A strain of Coprinellus curtus (designated GM-21), a basidiomycete that suppressed bottom-rot disease of Chinese cabbage, 'pak-choi' (Brassica campestris), caused by the pathogen Rhizoctonia solani Pak-choi 2 was isolated. The mechanism of plant disease suppression was discovered to be hyphal interference, a combative fungal interaction between strain GM-21 and the pathogen. The antifungal spectrum of strain GM-21 was shown to include R. solani and Fusarium sp., i.e. strain GM-21 showed disease-suppressive ability against bottom-rot disease of lettuce and Rhizoctonia-patch disease of mascarene grass caused by strains of R. solani. In addition, clear evidence of hyphal interference between strain GM-21 and Fusarium pathogens that cause crown (foot) and root-rot disease of tomato and Fusarium wilt of melon, respectively, was demonstrated. It was thus considered that GM-21 is effective for suppressing soil-borne pathogens, and that GM-21 presents new possibilities for biological control of vegetable diseases. PMID:17850327

Roselle, or Jamaica sorrel (Hibiscus sabdariffa) is a popular vegetable in many tropical regions, cultivated for its leaves, seeds, stems and calyces which, the dried calyces are used to prepare tea, syrup, jams and jellies and as beverages. The main objectives of this study were to identify and characterise fungal pathogens associated with Roselle diseases based on their morphological and cultural characteristics and to determine the pathogenicity of four fungi infecting Roselle seedlings, namely Phoma exigua, Fusarium nygamai, Fusarium tgcq and Rhizoctonia solani in Penang. A total of 200 fungal isolates were obtained from 90 samples of symptomatic Roselle tissues. The isolates were identified based on cultural and morphological characteristics, as well as their pathogenicity. The fungal pathogen most frequently isolated was P. exigua (present in 45% of the samples), followed by F. nygamai (25%), Rhizoctonia solani (19%) and F. camptoceras (11%). Pathogenicity tests showed that P. exigua, F. nygamai, F. camptoceras and R. solani were able to infect both wounded and unwounded seedlings with different degrees of severity as indicated by the Disease severity (DS). R. solani was the most pathogenic fungus affecting both wounded and unwounded Roselle seedlings, followed by P. exigua that was highly pathogenic on wounded seedlings. F. nygamai was less pathogenic while the least pathogenic fungus was F. camptoceras, infecting only the unwounded seedlings but, surprisingly, not the wounded plants. PMID:21839160

Plant tissue colonization by Trichoderma atroviride plays a critical role in the reduction of diseases caused by phytopathogenic fungi, but this process has not been thoroughly studied in situ. We monitored in situ interactions between gfp-tagged biocontrol strains of T. atroviride and soilborne plant pathogens that were grown in cocultures and on cucumber seeds by confocal scanning laser microscopy and fluorescence stereomicroscopy. Spores of T. atroviride adhered to Pythium ultimum mycelia in coculture experiments. In mycoparasitic interactions of T. atroviride with P. ultimum or Rhizoctonia solani, the mycoparasitic hyphae grew alongside the pathogen mycelia, and this was followed by coiling and formation of specialized structures similar to hooks, appressoria, and papillae. The morphological changes observed depended on the pathogen tested. Branching of T. atroviride mycelium appeared to be an active response to the presence of the pathogenic host. Mycoparasitism of P. ultimum by T. atroviride occurred on cucumber seed surfaces while the seeds were germinating. The interaction of these fungi on the cucumber seeds was similar to the interaction observed in coculture experiments. Green fluorescent protein expression under the control of host-inducible promoters was also studied. The induction of specific Trichoderma genes was monitored visually in cocultures, on plant surfaces, and in soil in the presence of colloidal chitin or Rhizoctonia by confocal microscopy and fluorescence stereomicroscopy. These tools allowed initiation of the mycoparasitic gene expression cascade to be monitored in vivo. PMID:15128569

Suppressive soils are characterized by a very low level of disease development even though a virulent pathogen and susceptible host are present. Biotic and abiotic elements of the soil environment contribute to suppressiveness, however most defined systems have identified biological elements as primary factors in disease suppression. Many soils possess similarities with regard to microorganisms involved in disease suppression, while other attributes are unique to specific pathogen-suppressive soil systems. The organisms operative in pathogen suppression do so via diverse mechanisms including competition for nutrients, antibiosis and induction of host resistance. Non-pathogenic Fusarium spp. and fluorescent Pseudomonas spp. play a critical role in naturally occurring soils that are suppressive to Fusarium wilt. Suppression of take-all of wheat, caused by Gaeumannomyces graminis var. tritici, is induced in soil after continuous wheat monoculture and is attributed, in part, to selection of fluorescent pseudomonads with capacity to produce the antibiotic 2,4-diacetylphloroglucinol. Cultivation of orchard soils with specific wheat varieties induces suppressiveness to Rhizoctonia root rot of apple caused by Rhizoctonia solani AG 5. Wheat cultivars that stimulate disease suppression enhance populations of specific fluorescent pseudomonad genotypes with antagonistic activity toward this pathogen. Methods that transform resident microbial communities in a manner which induces natural soil suppressiveness have potential as components of environmentally sustainable systems for management of soilborne plant pathogens. PMID:12448751

This study evaluated the use of grass clippings discharged from golf courses as the raw material for production of a suppressive compost to control Rhizoctonia large-patch disease in mascarene grass. Bacillus subtilis N4, a mesophilic bacterium with suppressive effects on the pathogenic fungus Rhizoctonia solani AG2-2, was used as an inoculum in a procedure developed with the aim of controlling composting temperatures and inoculation timing. The population density of mesophilic bacteria in the raw material was reduced to around 5 log10 CFU/g (dry weight) of composting material in the self-heating reaction at the initial stage of composting by maintaining a temperature of 80°C for 1 day. The inoculum was applied immediately, and the composting material was maintained at 40°C for 3 days. This served both to highly concentrate the suppressive bacterium and to achieve sporulation. The temperature was then raised to 60°C and maintained, enabling hygienic, high-speed composting while maintaining the population density of the suppressive bacterium as high as 8 log10 CFU/g (dry weight) in the compost. The suppressiveness of compost made in this way was confirmed in a turf grass disease prevention assay. PMID:9758834

Soil bacteria can benefit from co-occurring soil fungi in respect of the acquisition of carbonaceous nutrients released by fungal hyphae and the access to novel territories in soil. Here, we investigated the capacity of the mycosphere-isolated bacterium Burkholderia terrae BS001 to comigrate through soil along with hyphae of the soil fungi Trichoderma asperellum, Rhizoctonia solani, Fusarium oxysporum, F. oxysporum pv lini, Coniochaeta ligniaria, Phanerochaete velutina, and Phallus impudicus. We used Lyophyllum sp. strain Karsten as the reference migration-inciting fungus. Bacterial migration through presterilized soil on the extending fungal hyphae was detected with six of the seven test fungi, with only Phallus impudicus not showing any bacterial transport. Much like with Lyophyllum sp. strain Karsten, intermediate (106–108 CFU g-1 dry soil) to high (>108 CFU g-1 dry soil) strain BS001 cell population sizes were found at the hyphal migration fronts of four fungi, i.e., T. asperellum, Rhizoctonia solani, F. oxysporum and F. oxysporum pv lini, whereas for two fungi, Coniochaeta ligniaria and Phanerochaete velutina, the migration responses were retarded and population sizes were lower (103–106 CFU g-1 dry soil). Consistent with previous data obtained with the reference fungus, migration with the migration-inciting fungi occurred only in the direction of the hyphal growth front. Remarkably, Burkholderia terrae BS001 provided protection from several antifungal agents to the canonical host Lyophyllum sp. strain Karsten. Specifically, this host was protected from Pseudomonas fluorescens strain CHA0 metabolites, as well as from the anti-fungal agent cycloheximide. Similar protection by strain BS001was observed for T. asperellum, and, to a lower extent, F. oxysporum and Rhizoctonia solani. The protective effect may be related to the consistent occurrence of biofilm-like cell layers or agglomerates at the surfaces of the protected fungi. The current study represents the first report of protection of soil fungi against antagonistic agents present in the soil provided by fungal-associated Burkholderia terrae cells.

Although several strains of B. subtilis with antifungal activity have been isolated worldwide, to date there are no published reports regarding the isolation of a native B. subtilis strain from strawberry plants in Mexico. A native bacterium (Bacillus subtilis 21) demonstrated in vitro antagonistic activity against different plant pathogenic fungi. Under greenhouse conditions, it was shown that plants infected with Rhizoctonia solani and Fusarium verticillioides and treated with B. subtilis 21 produced augment in the number of leaves per plant and an increment in the length of healthy leaves in comparison with untreated plants. In addition, B. subtilis 21 showed activity against pathogenic bacteria. Secreted proteins by B. subtilis 21 were studied, detecting the presence of proteases and bacteriocin-like inhibitor substances that could be implicated in its antagonistic activity. Chitinases and zwittermicin production could not be detected. Then, B. subtilis 21 could potentially be used to control phytopathogenic fungi that infect strawberry plants. PMID:22593682

Anti-microbial properties of 21 endophytic fungal strains from Hypericum perforatum Linn. were evaluated against three human pathogens, Staphyloccocus aureus, Escherichia coli and Rhodotorula glutinis, and two phytopathogens, Rhizoctonia cerealis and Pyricularia grisea. The results indicated that the ethyl acetate extracts of endophytic fermentation broth had stronger anti-microbial activities than their fermentation broth. And the inhibitory effect of the endophytic extracts on human pathogens was better than those on phytopathogens. Among these endophytic fungi, strains GYLQ-10, GYLQ-24 and GYLQ-22 respectively showed the strongest activities against S. aureu, E. coli, R. glutinis. GYLQ-14 and GYLQ-22 exhibited the most pronounced effect on P. Grisea while both GYLQ-06 and GYLQ-08 had the strongest anti-microbial activities against R. cerealis. Till now, this study is the first report on the isolation of endophytic fungi from H. perforatum Linn. and their anti-microbial evaluation. PMID:25176358

A new ?-lactone coumarin, named as excavarin-A, showing antifungal activity was isolated from the leaves of Clausena excavata by bioassay guided fractionation method. The structure was elucidated by spectroscopic data analysis and identified as 7((2E)-4(4,5-dihydro-3-methylene-2-oxo-5-furanyl)-3-methylbut-2-enyloxy) coumarin. Minimum inhibitory concentration (MIC) was determined against fifteen fungal strains pathogenic against plants and human. The least MIC was recorded against the human pathogen, Candida tropicalis and the plant pathogens Rhizoctonia solani and Sclerotinia sclerotiorum. Antifungal activities against the human pathogens, Aspergillus fumigatus and Mucor circinelloides and plant pathogens, Colletotrichum gloeosporioides, Lasiodiplodia theobromae, Fusarium oxysporum and Rhizopus stolonifer were stronger than that of the standard antimicrobials. PMID:22088496

A survey of the post-harvest fruit rot diseases of tomato was conducted in five states of Nigeria. During severe infections, the diseases could cause 25% loss at harvest and 34% loss of the remaining product in transit, storage and market stalls; thus giving an overall loss of about 50% of the product. Two types of rots, soft and dry were recognised. The soft rot was found to account for about 85% and the dry rot about 15% of the overall loss. Erwinia carotovora, Rhizopus oryzae, R. stolonifer, Fusarium equiseti, F. nivale and F. oxysporum were established as the soft rot pathogens; while Aspergillus aculeatus, A. flavus, Cladosporium tenuissimum, Corynespora cassiicola, Curvularia lunata, Penicillium expansum P. multicolor and Rhizoctonia solani were established as the dry rot pathogens of tomato fruits in Nigeria. PMID:471028

Bioassay-guided separation with an eye toward antifungal activity led to the isolation of the new alkaloid 5-(1?,1?-dimethylallyl)-8-hydroxyfuro[2-3-b] quinoline (1) and the known biscoumarin daphnoretin (2) as the active constituents of the chloroform extract obtained from the leaves of Ruta chalepensis. The structures of the metabolites were elucidated on the basis of their spectral characteristics (NMR, UV, and MS) and were compared with the literature. The antifungal activity of the isolated compounds was evaluated against the phytopathogenic fungi Rhizoctonia solani, Sclerotium rolfsii, and Fusarium solani, which cause root-rot and wilt diseases in several economically important food crops such as potato, sugar beet, and tomato. PMID:22491304

Establishment of symbiotic association at the appropriate developmental stage helped maintain continued growth which is vital for the long-term ex vitro survival of the orchid. In the present study, symbiotic association was carried out using different developmental stages of Dendrobium chrysanthum and pathogenic Rhizoctonia isolates (obtained from orchids and non-orchid hosts) in different culture media. Isolate 2162 supported highest symbiotic germination on OMA-S (oat meal agar medium without nutrients?+?sucrose), whereas, stable symbiotic association with plantlets was obtained with isolate 4634 on OMA-NC (oat meal agar medium?+?cellulose). Isolate Dc-2S2 obtained from the host plant did not promote seed germination nor did it form association with protocorms or plantlets. This study, for the first time identifies a combination of compatible fungal isolate, suitable culture medium, and appropriate developmental stage at which symbiotic association in vitro can be deemed successful for the medicinally important orchid, D. chrysanthum. PMID:23553724

A cytochemical study was made to examine the possibility that acid phosphatase may be specifically involved in the digestion of endophytic hyphae in orchid mycorrhiza. Esterase activity was studied for comparison. Frozen sections of unfixed or glutaraldehyde-fixed protocorms of Dactylorhiza purpurella infected by Thanatephorus cucumeris (Rhizoctonia solani) were reacted for acid naphthol AS BI phosphatase, acid ?-glycerophosphatase or naphthol AS D esterase.A marked increase in particulate acid naphthol AS BI phosphatase activity was observed during infection of host, central, parenchyma cells shortly before hyphae lysed; a diffuse reaction of high activity was localised on lysed fungus. Acid ?-glycerophosphatase was present at particulate sites only in fungal cytoplasm and as a diffuse reaction on lysed fungus.Naphthol AS D esterase showed highest activity at hyphal apices. Esterase seems to be associated with growth and differentiation of hyphae in orchid cells, rather than lysis of the fungus. PMID:24469896

Sheath blight caused by Rhizoctonia solani (teleomorph: Thanatephorus cucumeris) is a major cause of crop loss in intensive rice production systems. No economically viable control methods have been developed. We screened aqueous extracts of common herbal plants that could reduce sheath blight lesions and found that foliar spraying and seed soaking application of extracts of either fresh or dried leaves of Chromolaena odorata gave up to 68% reduction in sheath blight lesion lengths under controlled and semi-field conditions. The observed reductions were not dependent on growth conditions of C. odorata and rice cultivar. The effect was observed until 21 days after inoculation and was not dependent on microbial activity. Under semi-field conditions, extracts also reduced severity of other important rice diseases, i.e., blast (Pyricularia oryzae) using foliar spray (up to 45%), brown spot (Bipolaris oryzae) using seed treatment (up to 57%), and bacterial blight (Xanthomonas oryzae pv. oryzae) using both application methods (up to 50%). PMID:20839964

Elimination of Criconemoides xenoplax from a prune orchard soil by fumigation with ethylene dibromide at the rate of 42 muliter/liter of soil (equivalent to about 13 gal/acre) improved the growth of Myrobalan plum, Addition of this nematode to Myrobalan seedlings or young 'Marianna 2624' plants propagated from cuttings resulted in destruction of cortical root tissue, darkening of roots, alteration of water stress, lowering of nutrient levels in leaves, and reduction in plant weight. C. xenoplax increased on all nine Prunus cerasifera varieties and hybrids tested, including those used commonly as rootstocks for prunes and plums. Rhizoctonia solani isolated from Myrobalan seedlings infected with C. xenoplax caused lesions on the hypocotyls of young Myrobalan seedlings in the laboratory, but had no effect on older seedlings in the greenhouse, and did not alter the effect of C. xenoplax. PMID:19308143

The use of antagonist microorganisms against fungal plant pathogens is an attractive and ecologically alternative to the use of chemical pesticides. Streptomyces are beneficial soil bacteria and potential candidates for biocontrol agents. This study reports the isolation, characterization and antagonist activity of soil streptomycetes from the Los Petenes Biosphere Reserve, a Natural protected area in Campeche, Mexico. The results showed morphological, physiological and biochemical characterization of six actinomycetes and their inhibitory activity against Curvularia sp., Aspergillus niger, Helminthosporium sp. and Fusarium sp. One isolate, identified as Streptomyces sp. CACIS-1.16CA showed the potential to inhibit additional pathogens as Alternaria sp., Phytophthora capsici, Colletotrichum sp. and Rhizoctonia sp. with percentages ranging from 47 to 90 %. This study identified a streptomycete strain with a broad antagonist activity that could be used for biocontrol of plant pathogenic fungi. PMID:24310522

Disease resistance in transgenic plants has been improved, for the first time, by the insertion of a gene from a biocontrol fungus. The gene encoding a strongly antifungal endochitinase from the mycoparasitic fungus Trichoderma harzianum was transferred to tobacco and potato. High expression levels of the fungal gene were obtained in different plant tissues, which had no visible effect on plant growth and development. Substantial differences in endochitinase activity were detected among transformants. Selected transgenic lines were highly tolerant or completely resistant to the foliar pathogens Alternaria alternata, A. solani, Botrytis cinerea, and the soilborne pathogen Rhizoctonia solani. The high level and the broad spectrum of resistance obtained with a single chitinase gene from Trichoderma overcome the limited efficacy of transgenic expression in plants of chitinase genes from plants and bacteria. These results demonstrate a rich source of genes from biocontrol fungi that can be used to control diseases in plants. PMID:9653105

Sheath blight, caused by Rhizoctonia solani, is one of the most serious diseases of rice. Among 33 rice accessions, mainly from National Institute of Agrobiological Sciences (NIAS) Core Collection, we found three landraces from the Himalayas—Jarjan, Nepal 555 and Nepal 8—with resistance to sheath blight in 3 years’ field testing. Backcrossed inbred lines (BILs) derived from a cross between Jarjan and the leading Japanese cultivar Koshihikari were used in QTL analyses. Since later-heading lines show fewer lesions, we used only earlier-heading BILs to avoid association with heading date. We detected eight QTLs; the Jarjan allele of three of these increased resistance. Only one QTL, on chromosome 9 (between markers Nag08KK18184 and Nag08KK18871), was detected in all 3 years. Chromosome segment substitution lines (CSSLs) carrying it showed resistance in field tests. Thirty F2 lines derived from a cross between Koshihikari and one CSSL supported the QTL. PMID:24273425

Bacillus subtitles JA isolated by our laboratory produced a large amount of antifungal substances, which had strong inhibitory activity against various plant pathogenic fungi, such as Rhizoctonia solani, Fusarium graminearum and so on. Ion beam implantation as a new mutagenic methods was applied in our studay. After B. subtitles JA was implanted by N+ ions, a strain designated as B. subtitles JA-026 was screened and obtained, which had a higher ability to produce those antifungal substances. A series of experiments indicated that the antifungal substances were thermostable and partially sensitive to proteinases K and tryproteinase. When the fermentating broth was fractionated with ammonium sulphate of a final saturation of 70%, the precipitate-enhanced inhibitory activity while the supernatant lost this activity. It appeared that the antifungal substances were likely to be protein.

Herbicide resistant weed populations have developed due to the repeated application of herbicides. Elevated concentrations of atmospheric CO2 can have positive effects on weed growth, but how rising CO2 might affect herbicide resistant weeds is not known. Ragweed (Ambrosia artemisiifolia L.) ecotypes known to be resistant or susceptible to glyphosate herbicide were exposed to either ambient or elevated (ambient +200 ? mol mol(-1)) concentrations of CO2 in open top chambers. Plants were harvested following 8 weeks of CO2 exposure; at this time, they had begun to exhibit disease symptoms including spots on leaves and stems. Elevated CO2 significantly increased top, root, and total plant biomass. Also, glyphosate resistant plants had significantly greater top, root, and total biomass than plants susceptible to the herbicide. There were no significant CO2 by ecotype interactions. Fungi from 13 genera were associated with ragweed, several of which can be either pathogens (i.e., Alternaria, Fusarium, Rhizoctonia), aiding the decline in health of the ragweed plants, or saprophytes existing on dead plant tissues. The common foliar disease powdery mildew was significantly higher on susceptible compared with resistant ragweed. Susceptible plants also showed an increased frequency of Rhizoctonia on leaves and Alternaria on stems; however, Fusarium occurred more frequently on resistant ragweed leaves. Fungi were not affected by CO2 concentration or its interaction with ecotype. This study reports the first information on the effects of elevated CO2 on growth of herbicide resistant weeds. This is also the first study examining the impact of herbicide resistance and elevated CO2 on fungi associated with weeds. What effects herbicide resistance might have on plant diseases and how rising atmospheric CO2 might impact these effects needs to be addressed, not only with important weeds but also with crops. PMID:25309569

Natural biological suppression of soil-borne diseases is a function of the activity and composition of soil microbial communities. Soil microbe and phytopathogen interactions can occur prior to crop sowing and/or in the rhizosphere, subsequently influencing both plant growth and productivity. Research on suppressive microbial communities has concentrated on bacteria although fungi can also influence soil-borne disease. Fungi were analyzed in co-located soils ‘suppressive’ or ‘non-suppressive’ for disease caused by Rhizoctonia solani AG 8 at two sites in South Australia using 454 pyrosequencing targeting the fungal 28S LSU rRNA gene. DNA was extracted from a minimum of 125 g of soil per replicate to reduce the micro-scale community variability, and from soil samples taken at sowing and from the rhizosphere at 7 weeks to cover the peak Rhizoctonia infection period. A total of ?994,000 reads were classified into 917 genera covering 54% of the RDP Fungal Classifier database, a high diversity for an alkaline, low organic matter soil. Statistical analyses and community ordinations revealed significant differences in fungal community composition between suppressive and non-suppressive soil and between soil type/location. The majority of differences associated with suppressive soils were attributed to less than 40 genera including a number of endophytic species with plant pathogen suppression potentials and mycoparasites such as Xylaria spp. Non-suppressive soils were dominated by Alternaria, Gibberella and Penicillum. Pyrosequencing generated a detailed description of fungal community structure and identified candidate taxa that may influence pathogen-plant interactions in stable disease suppression. PMID:24699870

Orchids typically depend on fungi for establishment from seeds, forming mycorrhizal associations with basidiomycete fungal partners in the polyphyletic group rhizoctonia from early stages of germination, sometimes with very high specificity. This has raised important questions about the roles of plant and fungal phylogenetics, and their habitat preferences, in controlling which fungi associate with which plants. In this issue of Molecular Ecology, Martos et al. (2012) report the largest network analysis to date for orchids and their mycorrhizal fungi, sampling a total of over 450 plants from nearly half the 150 tropical orchid species on Reunion Island, encompassing its main terrestrial and epiphytic orchid genera. The authors found a total of 95 operational taxonomic units of mycorrhizal fungi and investigated the architecture and nestedness of their bipartite networks with 73 orchid species. The most striking finding was a major ecological barrier between above- and belowground mycorrhizal fungal networks, despite both epiphytic and terrestrial orchids often associating with closely related taxa across all three major lineages of rhizoctonia fungi. The fungal partnerships of the epiphytes and terrestrial species involved a diversity of fungal taxa in a modular network architecture, with only about one in ten mycorrhizal fungi partnering orchids in both groups. In contrast, plant and fungal phylogenetics had weak or no effects on the network. This highlights the power of recently developed ecological network analyses to give new insights into controls on plant-fungal symbioses and raises exciting new hypotheses about the differences in properties and functioning of mycorrhiza in epiphytic and terrestrial orchids. PMID:23057699

ABSTRACT Apple replant disease typically is managed through pre-plant application of broad-spectrum soil fumigants including methyl bromide. The impending loss or restricted use of soil fumigants and the needs of an expanding organic tree fruit industry necessitate the development of alternative control measures. The microbial community resident in a wheat field soil was shown to suppress components of the microbial complex that incites apple replant disease. Pseudomonas putida was the primary fluorescent pseudomonad recovered from suppressive soil, whereas Pseudomonas fluorescens bv. III was dominant in a conducive soil; the latter developed within 3 years of orchard establishment at the same site. In greenhouse studies, cultivation of wheat in replant orchard soils prior to planting apple suppressed disease development. Disease suppression was induced in a wheat cultivar-specific manner. Wheat cultivars that enhanced apple seedling growth altered the dominant fluorescent pseudo-monad from Pseudomonas fluorescens bv. III to Pseudomonas putida. The microbial community resident in replant orchard soils after growing wheat also was suppressive to an introduced isolate of Rhizoctonia solani anastomosis group 5, which causes root rot of apple. Incorporation of high glucosinolate containing rapeseed ('Dwarf Essex') meal also enhanced growth of apple in replant soils through suppression of Rhizoc-tonia spp., Cylindrocarpon spp., and Pratylenchus penetrans. Integration of these methods will require knowledge of the impact of the biofumigant component on the wheat-induced disease-suppressive microbial community. Implementation of these control strategies for management of apple replant disease awaits confirmation from ongoing field validation trials. PMID:18943894

ABSTRACT The effect of seed meals derived from Brassica juncea, B. napus, or Sinapis alba on suppression of soilborne pathogens inciting replant disease of apple was evaluated in greenhouse trials. Regardless of plant source, seed meal amendment significantly improved apple growth in all orchard soils; however, relative differences in pathogen suppression were observed. All seed meals suppressed root infection by native Rhizoctonia spp. and an introduced isolate of Rhizoctonia solani AG-5, though B. juncea seed meal often generated a lower level of disease control relative to other seed meal types. When introduction of the pathogen was delayed until 4 to 8 weeks post seed meal amendment, disease suppression was associated with proliferation of resident Streptomyces spp. and not qualitative or quantitative attributes of seed meal glucosinolate content. Using the same experimental system, when soils were pasteurized prior to pathogen infestation, control of R. solani was eliminated regardless of seed meal type. In the case of B. juncea seed meal amendment, the mechanism of R. solani suppression varied in a temporal manner, which initially was associated with the generation of allylisothiocyanate and was not affected by soil pasteurization. Among those tested, only B. juncea seed meal did not stimulate orchard soil populations of Pythium spp. and infection of apple roots by these oomycetes. Although application of B. napus seed meal alone consistently induced an increase in Pythium spp. populations, no significant increase in Pythium spp. populations was observed in response to a composite B. juncea and B. napus seed meal amendment. Suppression of soil populations and root infestation by Pratylenchus spp. was dependent upon seed meal type, with only B. juncea providing sustained nematode control. Collectively, these studies suggest that use of a composite B. juncea and B. napus seed meal mixture can provide superior control of the pathogen complex inciting apple replant disease relative to either seed meal used alone. PMID:18943286

Herbicide resistant weed populations have developed due to the repeated application of herbicides. Elevated concentrations of atmospheric CO2 can have positive effects on weed growth, but how rising CO2 might affect herbicide resistant weeds is not known. Ragweed (Ambrosia artemisiifolia L.) ecotypes known to be resistant or susceptible to glyphosate herbicide were exposed to either ambient or elevated (ambient +200 ? mol mol?1) concentrations of CO2 in open top chambers. Plants were harvested following 8 weeks of CO2 exposure; at this time, they had begun to exhibit disease symptoms including spots on leaves and stems. Elevated CO2 significantly increased top, root, and total plant biomass. Also, glyphosate resistant plants had significantly greater top, root, and total biomass than plants susceptible to the herbicide. There were no significant CO2 by ecotype interactions. Fungi from 13 genera were associated with ragweed, several of which can be either pathogens (i.e., Alternaria, Fusarium, Rhizoctonia), aiding the decline in health of the ragweed plants, or saprophytes existing on dead plant tissues. The common foliar disease powdery mildew was significantly higher on susceptible compared with resistant ragweed. Susceptible plants also showed an increased frequency of Rhizoctonia on leaves and Alternaria on stems; however, Fusarium occurred more frequently on resistant ragweed leaves. Fungi were not affected by CO2 concentration or its interaction with ecotype. This study reports the first information on the effects of elevated CO2 on growth of herbicide resistant weeds. This is also the first study examining the impact of herbicide resistance and elevated CO2 on fungi associated with weeds. What effects herbicide resistance might have on plant diseases and how rising atmospheric CO2 might impact these effects needs to be addressed, not only with important weeds but also with crops. PMID:25309569

Naturally occurring disease-suppressive soils have been documented in a variety of cropping systems, and in many instances the biological attributes contributing to suppressiveness have been identified. While these studies have often yielded an understanding of operative mechanisms leading to the suppressive state, significant difficulty has been realized in the transfer of this knowledge into achieving effective field-level disease control. Early efforts focused on the inundative application of individual or mixtures of microbial strains recovered from these systems and known to function in specific soil suppressiveness. However, the introduction of biological agents into non-native soil ecosystems typically yielded inconsistent levels of disease control. Of late, greater emphasis has been placed on manipulation of the cropping system to manage resident beneficial rhizosphere microorganisms as a means to suppress soilborne plant pathogens. One such strategy is the cropping of specific plant species or genotypes or the application of soil amendments with the goal of selectively enhancing disease-suppressive rhizobacteria communities. This approach has been utilized in a system attempting to employ biological elements resident to orchard ecosystems as a means to control the biologically complex phenomenon termed apple replant disease. Cropping of wheat in apple orchard soils prior to re-planting the site to apple provided control of the fungal pathogen Rhizoctonia solani AG-5. Disease control was elicited in a wheat cultivar-specific manner and functioned through transformation of the fluorescent pseudomonad population colonizing the rhizosphere of apple. Wheat cultivars that induced disease suppression enhanced populations of specific fluorescent pseudomonad genotypes with antagonistic activity toward R. solani AG-5, but cultivars that did not elicit a disease-suppressive soil did not modify the antagonistic capacity of this bacterial community. Alternatively, brassicaceae seed meal amendments were utilized to develop soil suppressiveness toward R. solani. Suppression of Rhizoctonia root rot in response to seed meal amendment required the activity of the resident soil microbiota and was associated with elevated populations of Streptomyces spp. recovered from the apple rhizosphere. Application of individual Streptomyces spp. to soil systems provided control of R. solani to a level and in a manner equivalent to that obtained with the seed meal amendment. These and other examples suggest that management of resident plant-beneficial rhizobacteria may be a viable method for control of specific soilborne plant pathogens. PMID:19259490

Suppression of soil-borne plant pathogens with compost has been widely studied. Compost has been found to be suppressive against several soil-borne pathogens in various cropping systems. However, an increase of some diseases due to compost usage has also been observed, since compost is a product that varies considerably in chemical, physical and biotic composition, and, consequently, also in ability to suppress soil borne diseases. New opportunities in disease management can be obtained by the selection of antagonists from suppressive composts. The objective of the present work was to isolate microorganisms from a suppressive compost and to test them for their activity against soil-borne pathogens. A compost from green wastes, organic domestic wastes and urban sludge's that showed a good suppressive activity in previous trials was used as source of microorganisms. Serial diluted suspensions of compost samples were plated on five different media: selective for Fusarium sp., selective for Trichoderma sp., selective for oomycetes, potato dextrose agar (PDA) for isolation of fungi, lysogeny broth (LB) for isolation of bacteria. In total, 101 colonies were isolated from plates and tested under laboratory conditions on tomato seedlings growing on perlite medium in Petri plates infected with Fusarium oxysporum f.sp. radicis-lycopersici and compared to a commercial antagonist (Streptomyces griserovidis, Mycostop, Bioplanet). Among them, 28 showed a significant disease reduction and were assessed under greenhouse condition on three pathosystems: Fusarium oxysporum f.sp. basilica/basil, Phytophthora nicotianae/tomato and Rhizoctonia solani/bean. Fusarium spp. selected from compost generally showed a good disease control against Fusarium wilts, while only bacteria significantly controlled P. nicotianae on tomato under greenhouse conditions. None of the microorganisms was able to control the three soil-borne pathogens together, in particular Rhizoctonia solani. Results confirmed the good suppressive activity of the compost under study against soil-borne pathogens. The selection of antagonists from compost is a promising strategy for the development of new biological control agents against soil-borne pathogens. PMID:21534476

Naturally existing biological materials have been garning considerable attention as environmentally benign green-nanofactories for the fabrication of diverse nanomaterials, and with desired size and shape distributions. In the present investigation, we report the size and shape controllable biofabrication of silver nanocrystallites using the growth extract of the fungus, Rhizoctonia solani. Influence of various factors such as growth medium; radiation, in the form of sun light; and seeding duration on the production of silver nanoparticles using aqueous 1 mm silver nitrate solution under ambient conditions is presented. Our results demonstrate that these factors can significantly influence the production, size and shape transformation, and the rate of nanoparticles formation. Multiple characterization techniques involving UV-visible and Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and transmission electron microscopy measurements confirmed the production, surface and structural characteristics, purity and crystalline nature of the biosynthesized silver nanoparticles. Our biogenic synthesis process provides a simple, ecologically friendly, cost-effective synthesis route, and most importantly the ability to have control over the size and shape distributions that lends itself for various biomedical and opto-electronic applications. PMID:23755682

ABSTRACT To detect molecules with elicitor properties from Pythium oligandrum, cell wall protein fractions (CWPs) were extracted from 10 P. oligandrum isolates and examined for elicitor activity in sugar beet and wheat. P. oligandrum isolates were divided into two groups based on the number of major proteins in CWP: isolates with two major proteins (D-type) and isolates with one major protein (S-type). Sugar beet seedlings treated with both types of CWP through their roots showed enhanced activities of phenylalanine ammonia lyase and chitinase, and D-type-treated seedlings also showed significantly higher cell wall-bound phenolic compounds, mainly ferulic acid, compared with the distilled-water-treatment control. Damping-off severity was significantly reduced on seedlings treated with both types of CWP compared with the control, following challenge with Rhizoctonia solani AG2-2. Both types of CWP significantly reduced the number of infected spikelets developed from the injected spikelet compared with the control, following challenge with Fusarium graminearum. Neither type of CWP resulted in any reduction in pathogen growth rate in plate tests. These results demonstrate that CWPs of P. oligandrum have elicitor properties in sugar beet and wheat. PMID:18944321

Creeping bentgrass (Agrostis stolonifera L.) is one of the most adapted bentgrass species for use on golf course fairways and putting greens because of its high tolerance to low mowing height. It is a highly outcrossing allotetraploid species (2n=4x=28, A(2) and A(3) subgenomes). The first linkage map in this species is reported herein, and it was constructed based on a population derived from a cross between two heterozygous clones using 169 RAPD, 180 AFLP, and 39 heterologous cereal and 36 homologous bentgrass cDNA RFLP markers. The linkage map consists of 424 mapped loci covering 1,110 cM in 14 linkage groups, of which seven pairs of homoeologous chromosomes were identified based on duplicated loci. The numbering of all seven linkage groups in the bentgrass map was assigned according to common markers mapped on syntenous chromosomes of ryegrass and wheat. The number of markers linked in coupling and repulsion phase was in a 1:1 ratio, indicating disomic inheritance. This supports a strict allotetraploid inheritance in creeping bentgrass, as suggested by previous work based on chromosomal pairing and isozymes. This linkage map will assist in the tagging and eventually in marker-assisted breeding of economically important quantitative traits like disease resistance to dollar spot (Sclerotinia homoeocarpa F.T. Bennett) and brown patch (Rhizoctonia solani Kuhn). PMID:15981010

Four rhizobacteria selected out of over 500 isolates from rhizosphere of the vegetables in China were further studied for suppression of the root-knot nematode and soil-borne fungal pathogens in laboratory and greenhouse in Belgium. They were identified as Brevibacillus brevis or Bacillus subtilis by Biolog test and partial 16s rDNA sequence comparison. They not only inhibited the radial growth of the root-infecting fungi Rhizoctonia solani SX-6, Pythium aphanidermatum ZJP-1 and Fusarium oxysporum f.sp. cucumerinum ZJF-2 in vitro, but also exhibited strong nematicidal activity by killing the second stage larvae of Meloidogyne javanica to varying degrees in the greenhouse. The toxic principles of bacterium B7 that showed the highest juvenile mortality were partially characterized. The active factors were heat stability and resistance to extreme pH values. B7 used either as seed dressing or soil drench significantly reduced the nematode populations in the rhizosphere and enhanced the growth of mungbean plants over the controls in the presence or absence of R. solani. PMID:15909333

The use of beneficial soil microorganisms as agricultural inputs for improved crop production requires selection of rhizosphere-competent microorganisms with plant growth-promoting attributes. A collection of 563 bacteria originating from the roots of pea, lentil, and chickpea grown in Saskatchewan was screened for several plant growth-promoting traits, for suppression of legume fungal pathogens, and for plant growth promotion. Siderophore production was detected in 427 isolates (76%), amino-cyclopropane-1-carboxylic acid (ACC) deaminase activity in 29 isolates (5%), and indole production in 38 isolates (7%). Twenty-six isolates (5%) suppressed the growth of Pythium sp. strain p88-p3, 40 isolates (7%) suppressed the growth of Fusarium avenaceum, and 53 isolates (9%) suppressed the growth of Rhizoctonia solani CKP7. Seventeen isolates (3%) promoted canola root elongation in a growth pouch assay, and of these, 4 isolates promoted the growth of lentil and one isolate promoted the growth of pea. Fatty acid profile analysis and 16S rRNA sequencing of smaller subsets of the isolates that were positive for the plant growth-promotion traits tested showed that 39%-42% were members of the Pseudomonadaceae and 36%-42% of the Enterobacteriaceae families. Several of these isolates may have potential for development as biofertilizers or biopesticides for western Canadian legume crops. PMID:18388997

Although plant diseases can be caused by bacteria, viruses, and protists, most are caused by fungi and fungus-like oomycetes. Intensive use of fungicides with the same mode of action can lead to selection of resistant strains increasing the risk of unmanageable epidemics. In spite of the integrated use of nonchemical plant disease management strategies, agricultural productivity relies heavily on the use of chemical pesticides and biocides for disease prevention and treatment and sanitation of tools and substrates. Despite the prominent use of fungi in early hormesis studies and the continuous use of yeast as a research model, the relevance of hormesis in agricultural systems has not been investigated by plant pathologists, until recently. A protocol was standardized for detection and assessment of chemical hormesis in fungi and oomycetes using radial growth as endpoint. Biphasic dose-responses were observed in Pythium aphanidermatum exposed to sub-inhibitory doses of ethanol, cyazofamid, and propamocarb, and in Rhizoctonia zeae exposed to ethanol. This report provides an update on chemical hormesis in fungal plant pathogens and a perspective on the potential risks it poses to crop productivity and global food supply. PMID:23983664

In the current study, mycotoxicoses of ruminants and horses are reviewed, with an emphasis on the occurrence of these diseases in South America. The main mycotoxicoses observed in grazing cattle include intoxications by indole-diterpenoid mycotoxins (Paspalum spp. contaminated by Claviceps paspali, Lolium perenne infected by Neotyphodium lolii, Cynodon dactylon infected by Claviceps cynodontis, and Poa huecu), gangrenous ergotism and dysthermic syndrome (hyperthermia) caused by Festuca arundinacea (syn. Festuca elatior) infected by Neotyphodium coenophialum (syn. Acremonium coenophialum), and photosensitization in pastures contaminated by toxigenic Pithomyces chartarum. Other mycotoxicoses in grazing cattle include slaframine toxicity in clover pastures infected by Rhizoctonia leguminicola and diplodiosis in cattle grazing in corn stubbles. The mycotoxicoses caused by contaminated concentrated food or byproducts in cattle include poisoning by toxins of Aspergillus clavatus, which contaminate barley or sugar beetroot by-products, gangrenous ergotism or dysthermic syndrome caused by wheat bran or wheat screenings contaminated with Claviceps purpurea, and acute respiratory distress caused by damaged sweet potatoes (Ipomoea batatas). The main mycotoxicosis of horses is leukoencephalomalacia caused by the fumonisins B1 and B2 produced by Fusarium spp. Poisoning by C. purpurea and F. elatior infected by N. coenophialum has also been reported as a cause of agalactia and neonatal mortality in mares. Slaframine toxicosis caused by the ingestion of alfalfa hay contaminated by R. leguminicola has also been reported in horses. PMID:24091682

Sebacinales was described in 2004 and is currently recognized as the earliest diverging lineage of mycorrhizal Basidiomycota. In addition, recent research has demonstrated that no other known fungal order harbours a broader spectrum of mycorrhizal types. Yet because of the character poor morphology of these inconspicuous fungi, a reliable systematic framework for Sebacinales is still out of reach. In order to increase the body of comparative data on Sebacinales, we followed a polyphasic approach using a sampling of seven diverse Sebacinales strains, including several isolates of Australian orchid mycorrhizae, Piriformospora indica, and a multinucleate rhizoctonia isolated from a pot culture of Glomus fasciculatum (Williams 1985) with clover. We performed molecular phylogenetic analyses from candidate barcoding regions [rDNA: internal transcribed spacer (ITS)1-5.8-ITS2, 28S; translation elongation factor 1-? (TEF)], enzymatic profiling, genome size estimation by quantitative polymerase chain reaction (PCR), and karyotype analysis using pulsed field gel electrophoresis. Here, we report significant differences in the physiological and molecular parameters inferred from these morphologically very similar strains. Particularly, our results indicate that intron sequences of the TEF gene are useful markers for Sebacinales at the species level. As a first taxonomic consequence, we describe Piriformospora williamsii as a new member of the so far monotypic genus Piriformospora and show that this genus contains still undescribed species that were recently discovered as endophytes of field-collected specimens of Anthyllis, Medicago, and Lolium in Germany. PMID:22289766

The seed germination of orchids under natural conditions requires association with mycorrhizal fungi. Dendrobium nobile and Dendrobium chrysanthum are threatened orchid species in China where they are considered medicinal plants. For conservation and application of Dendrobium using symbiosis technology, we isolated culturable endophytic and mycorrhizal fungi colonized in the protocorms and adult roots of two species plants and identified them by morphological and molecular analyses (5.8S and nrLSU). Of the 127 endophytic fungi isolated, 11 Rhizoctonia-like strains were identified as Tulasnellales (three strains from protocorms of D. nobile), Sebacinales (three strains from roots of D. nobile and two strains from protocorms of D. chrysanthum) and Cantharellales (three strains from roots of D. nobile), respectively. In addition, species of Xylaria, Fusarium, Trichoderma, Colletotrichum, Pestalotiopsis, and Phomopsis were the predominant non-mycorrhizal fungi isolated, and their probable ecological roles in the Dendrobium plants are discussed. These fungal resources will be of great importance for the large-scale cultivation of Dendrobium plants using symbiotic germination technology and for the screening of bioactive metabolites from them in the future. PMID:21779810

The trend to search novel microbial natural biocides has recently been increasing in order to avoid the environmental pollution from use of synthetic pesticides. Among these novel natural biocides are the bioactive secondary metabolites of Burkholderia gladioli pv. agaricicola (Bga). The aim of this study is to determine antifungal activity of Bga strains against some phytopathogenic fungi. The fungicidal tests were carried out using cultures and cell-free culture filtrates against Botrytis cinerea, Aspergillus flavus, Aspergillus niger, Penicillium digitatum, Penicillium expansum, Sclerotinia sclerotiorum and Phytophthora cactorum. Results demonstrated that all tested strains exert antifungal activity against all studied fungi by producing diffusible metabolites which are correlated with their ability to produce extracellular hydrolytic enzymes. All strains significantly reduced the growth of studied fungi and the bacterial cells were more bioactive than bacterial filtrates. All tested Bulkholderia strains produced volatile organic compounds (VOCs), which inhibited the fungal growth and reduced the growth rate of Fusarium oxysporum and Rhizoctonia solani. GC/MS analysis of VOCs emitted by strain Bga 11096 indicated the presence of a compound that was identified as 1-methyl-4-(1-methylethenyl)-cyclohexene, a liquid hydrocarbon classified as cyclic terpene. This compound could be responsible for the antifungal activity, which is also in agreement with the work of other authors. PMID:23208371

The recent release of the genome sequences of a number of crop and model plant species has made it possible to define the genome organisation and functional characteristics of specific genes and gene families of agronomic importance. For instance, Sorghum bicolor, maize (Zea mays) and Brachypodium distachyon genome sequences along with the model grass species rice (Oryza sativa) enable the comparative analysis of genes involved in plant defence. Germin-like proteins (GLPs) are a small, functionally and taxonomically diverse class of cupin-domain containing proteins that have recently been shown to cluster in an area of rice chromosome 8. The genomic location of this gene cluster overlaps with a disease resistance QTL that provides defence against two rice fungal pathogens (Magnaporthe oryzae and Rhizoctonia solani). Studies showing the involvement of GLPs in basal host resistance against powdery mildew (Blumeria graminis ssp.) have also been reported in barley and wheat. In this mini-review, we compare the close proximity of GLPs in publicly available cereal crop genomes and discuss the contribution that these proteins, and their genome sequence organisation, play in plant defence. PMID:20683632

We have studied the effects of two polyamine biosynthetic inhibitors, alpha-difluoromethylornithine (DFMO) and alpha-difluoromethylarginine (DFMA), and of polyamines (PAs), alone and in combination, on mycelial growth and morphology of four phytopathogenic fungi: Botrytis sp, B. cinerea, Rhizoctonia solani and Monilinia fructicola. The inhibitors were added to a Czapek agar medium to get final concentrations of 0.1, 0.5 and 1.0 mM. DFMO and DFMA, suicide inhibitors of ornithine decarboxylase (ODC) and arginine decarboxylase (ADC) respectively, inhibited mycelial growth strongly; the effect was generally more pronounced with DFMA than with DFMO, but each fungus had its own response pattern. The addition of the PAs putrescine (Put) and spermidine (Spd) to the culture medium resulted in a promotion of growth. In Botrytis sp and Monilinia fructicola exposed to inhibitors plus PAs, mycelial growth was actually increased above control values. Mycelial morphology was altered and cell size dramatically reduced in plates containing inhibitors alone, whereas with PAs alone, or in combination with inhibitors, morphology was normal, but cell length and diameters increased considerably. These results suggest that PAs are essential for growth in fungal mycelia. The inhibition caused by DFMA may be due to its arginase-mediated conversion to DFMO.

Sheath blight is an emerging threat in rice cultivation. It is animportant disease caused by the soil-borne necrotrophic pathogenic fungus, Rhizoctonia solani Kühn. However, to date neither known major genes for quantitative resistance, nor any rice lines immune to this disease has been identified. The disease resistance is quantitative in nature. Numerous genes are involved in this resistance process. There are few quantitative trait loci (QTLs) detected conferring improved resistance against the disease. Teqing and Tetepshowimproved resistance having QTLs, qSB-9 and qSBR11-1, respectively. Since, these QTLs demonstrates additive effects, pyramiding of these QTLs might be an option to increase the sheath blight resistance in rice. Nine rice cultivars were screened at greenhouse conditions. Results showed that Tetep and Teqing had the lowest disease ratings. UKMRC2a new high yielding cultivar was as recipient parent. Crosses between UKMRC2 and Teqing, and UKMRC2 and Tetep were made and confirmed. Subsequently 4-way crosses between the two F1s were performed to develop pyramidal lines.

The soil-borne pathogen Rhizoctonia solani is responsible for crop losses on a wide range of important crops worldwide. The lack of effective control strategies and the increasing demand for organically grown food has stimulated research on biological control. The aim of the present study was to evaluate the rhizosphere competence of the commercially available inoculant Bacillus amyloliquefaciens FZB42 on lettuce growth and health together with its impact on the indigenous rhizosphere bacterial community in field and pot experiments. Results of both experiments demonstrated that FZB42 is able to effectively colonize the rhizosphere (7.45 to 6.61 Log 10 CFU g?1 root dry mass) within the growth period of lettuce in the field. The disease severity (DS) of bottom rot on lettuce was significantly reduced from severe symptoms with DS category 5 to slight symptom expression with DS category 3 on average through treatment of young plants with FZB42 before and after planting. The 16S rRNA gene based fingerprinting method terminal restriction fragment length polymorphism (T-RFLP) showed that the treatment with FZB42 did not have a major impact on the indigenous rhizosphere bacterial community. However, the bacterial community showed a clear temporal shift. The results also indicated that the pathogen R. solani AG1-IB affects the rhizosphere microbial community after inoculation. Thus, we revealed that the inoculant FZB42 could establish itself successfully in the rhizosphere without showing any durable effect on the rhizosphere bacterial community. PMID:23935892

The toxicity of three organophosphorous nematicides, imicyafos, fosthiazate and cadusafos, to non-target organisms in soil was evaluated. Imicyafos and fosthiazate had no significant inhibitory effect on the growth of fungal (Fusarium oxysporum f. sp. lactucae, Rhizoctonia solani and Trichoderma viride) and bacterial (Ralstonia solanacearum and Pseudomonas fluorescens) strains in media at 12.5 to 200 mg L(-1). Cadusafos, however, significantly inhibited the growth of all these strains except R. solanacearum. A pot test was conducted using a soil naturally infested with Pratylenchus penetrans, and treated with imicyafos or fosthiazate, which are less toxic to non-target organisms. The density of P. penetrans decreased to less than 10% of the control level after exposure to imicyafos and fosthiazate at 3 kg active ingredient ha(-1), the conventional dose. No significant effect was observed on the density of free-living nematodes, cellulose decomposition activity, microbial biomass evaluated with the ATP method and number of ammonia oxidizers between the soil treated with imicyafos or fosthiazate and the untreated control soil. Our results revealed that imicyafos and fosthiazate effectively suppressed a plant-parasitic nematode, P. penetrans, but had little impact on free-living nematodes and the soil microbial community. PMID:21558727

Cyclic voltammetric measurements were performed for Co(II), Ni(II), Cu(II) and Zn(II) complexes of 1 : 1 alternating copolymer, poly(3-nitrobenzylidene-1-naphthylamine-co-succinic anhydride) (L) and Ni(II) and Cu(II) complexes of 1 : 1 alternating copolymer, poly(3-nitrobenzylidene-1-naphthylamine-co-methacrylic acid) (L1). The in vitro biological screening effects of the investigated compounds were tested against the fungal species including Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans and bacterial species including Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa by well diffusion method. A comparative study of inhibition values of the copolymers and their complexes indicates that the complexes exhibit higher antimicrobial activity. Copper ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. The nuclease activity of the above metal complexes were assessed by gel electrophoresis assay and the results show that the copper complexes can cleave pUC18 DNA effectively in presence of hydrogen peroxide compared to other metal complexes. The degradation experiments using Rhodamine B dye indicate that the hydroxyl radical species are involved in the DNA cleavage reactions. PMID:23997637

Three hundred ninety five bacterial isolates were collected from canola Root and Rhizosphere in Golestan, Mazandaran, Guilan and Tehran provinces. At first, antagonistic effect of bacterial isolates on Rhizoctonia solani was studied using dual culture test assay. The results showed that 60 isolates had the ability to inhibit the growth of fungi on PDA medium. On the basis of the biochemical, physiological and morphological tests, isolates Pf41, Pf51, Pf411 and Pf412 were identified as Pseudomonas fluorescens, isolate Bu1 as Burkholderia cepacia, the isolates B1, B2, Bs44 and B6 were as Bacillus subtilis and S44, str45 as Streptomyces sp. Results of the studies on biocontrol mechanism showed that Isolates produced antibiotics and volatile metabolites that prevented the mycelial growth of the fungus. Also the isolates produced some of antimicrobial metabolites including hydrogen cyanide, protease and siderophore. Isolates effect inhibition of in vitro growth of the fungus. The effect of isolates on disease reduction in compare with control have significantly differentiated. None of the isolates were able completely to prevent disease occurrence. Isolates applied as soil treatment had a significantly higher disease control as compared to seed treatment. Isolates had considerable effect on reduction disease under the greenhouse conditions. PMID:23878984

Fresh rhizomes of Zingiber officinale (ginger), when subjected to steam distillation, yielded ginger oil in which curcumene was found to be the major constituent. The thermally labile zingiberene-rich fraction was obtained from its diethyl ether extract. Column chromatography of ginger oleoresin furnished a fraction from which [6]-gingerol was obtained by preparative TLC. Naturally occurring [6]-dehydroshogaol was synthesised following condensation of dehydrozingerone with hexanal, whereas zingerone and 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)butane were obtained by hydrogenation of dehydrozingerone with 10% Pd/C. The structures of the compounds were established by 1H NMR, 13C NMR and mass (EI-MS and ES-MS) spectral analysis. The test compounds exhibited moderate insect growth regulatory (IGR) and antifeedant activity against Spilosoma obliqua, and significant antifungal activity against Rhizoctonia solani. Among the various compounds, [6]-dehydroshogaol exhibited maximum IGR activity (EC50 3.55 mg ml-1), while dehydrozingerone imparted maximum antifungal activity (EC50 86.49 mg litre-1). PMID:11455660

LC-MS/MS has demonstrated potential for detecting plant pathogens. Unlike PCR or ELISA, LC-MS/MS does not require pathogen-specific reagents for the detection of pathogen-specific proteins and peptides. However, the MS/MS approach we and others have explored does require a protein sequence reference database and database-search software to interpret tandem mass spectra. To evaluate the limitations of database composition on pathogen identification, we analyzed proteins from cultured Ustilago maydis, Phytophthora sojae, Fusarium graminearum, and Rhizoctonia solani by LC-MS/MS. When the search database did not contain sequences for a target pathogen, or contained sequences to related pathogens, target pathogen spectra were reliably matched to protein sequences from nontarget organisms, giving an illusion that proteins from nontarget organisms were identified. Our analysis demonstrates that when database-search software is used as part of the identification process, a paradox exists whereby additional sequences needed to detect a wide variety of possible organisms may lead to more cross-species protein matches and misidentification of pathogens. PMID:17922518

Over the past several decades, breeding cool-season turfgrasses for improved disease resistance has been the focus of many turfgrass breeding programs. This review article discusses the dramatic improvements made in breeding Kentucky bluegrass (Poa pratensis) for resistance to leaf spot (caused by Drechslera poae), stem rust (caused by Puccinia graminis), and stripe smut (caused by Ustilago striiformis); perennial ryegrass (Lolium perenne) for resistance to gray leaf spot (caused by Pyricularia grisea), stem rust and crown rust (caused by Puccinia coronata); tall fescue (Festuca arundinacea) for resistance to brown patch (Rhizoctonia solani) and stem rust; creeping bentgrass (Agrostis stolonifera) for resistance to dollar spot (caused by Sclerotinia homoeocarpa); and fine fescues (Festuca spp.) for improved disease resistance. Historically, the dramatic improvements in disease resistance of the cool-season grasses have been attributed to traditional/conventional breeding techniques; however, it is likely that functional genomics and molecular techniques will play a more significant role in the development of cultivated turfgrasses as the specific genes and mechanisms for disease resistance are identified in the future. PMID:17061916

The bacterial strain T-9, which shows strong antifungal activity, is isolated from the soils of Samcheok, Gangwondo and identified as Paenibacillus kribbensis according to morphological and taxonomic characteristics and 16S rRNA gene sequence analysis. The P. kribbensis strain T-9 strongly inhibits the growth of various phytopathogenic fungi including Botrytis cinerea, Colletotricum acutatum, Fusarium oxysporum f. sp. radicis-lycopersici, Magnaporthe oryzae, Phytophthora capsici, Rhizoctonia solani, and Sclerotium cepivorum in vitro. Also, the P. kribbensis strain T-9 exhibited similar or better control effects to plant diseases than in fungicide treatment through in vivo assays. In the 2-year greenhouse experiments, P. kribbensis strain T-9 was highly effective against clubroot. In the 2-year field trials, the P. kribbensis strain T-9 was less effective than the fungicide, but reduced clubroot on Chinese cabbage when compared to the control. The above-described results indicate that the strain T-9 may have the potential as an antagonist to control various phytopathogenic fungi. PMID:25288992

Phytase-producing bacteria (PPB) is being investigated as plant growth promoting rhizobacteria (PGPR) to improve the phosphorus (P) nutrition and growth of plants grown in soil with high phytate content. Phytate is dominant organic P forms in many soils and must be hydrolyzed to be available for plants. Indian mustard (Brassica juncea) is a plant with economic importance in agriculture and phytoremediation, therefore biotechnological tools to improve growth and environmental stress tolerance are needed. In this study, we isolated and characterized PPB from Himalayan soils and evaluated their effect on growth and P uptake by B. juncea under greenhouse conditions. Sixty five PPB were isolated and based on phytate hydrolysis, three efficient PPB were chosen and identified as Acromobacter sp. PB-01, Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13. Selected PPB showed ability to grow at wide range of pH, temperature and salt concentrations as well as to harbour diverse PGPR activities, such as: solubilization of insoluble Ca-phosphate (193-642 ?g ml(-1)), production of phytohormone indole acetic acid (5-39 ?g ml(-1)) and siderophore. Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13 showed 50 and 70 % inhibition of phytopathogen Rhizoctonia solani, respectively. Greenhouse potting assay also showed that the bacterization of B. juncea seeds with Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13 significantly increased the biomass and P content in 30 days old seedlings. This study reveals the potential of PPB as PGPR to improve the growth of B. juncea. PMID:23546828

A bioactivity-guided approach was employed to isolate and determine the chemical identity of bioactive constituents with antifungal activity from Actinoplanes sp. HBDN08. The structure of the antifungal metabolite was elucidated as 5-hydroxyl-5-methyl-2-hexenoic acid on the basis of spectral analysis. This compound showed strong in vitro antifungal activity against Botrytis cinerea, Cladosporium cucumerinum and Corynespora cassiicola, with an IC(50) of 32.45, 27.17, and 30.66 mg/L, respectively; however, it only moderately inhibited hyphal growth of Rhizoctonia solani with an IC(50) of 61.64 mg/L. The in vivo antifungal activity under greenhouse conditions demonstrated that 5-hydroxyl-5-methyl-2-hexenoic acid could effectively control the diseases caused by B. cinerea, C. cucumerinum and C. cassiicola with 71.42%, 78.63% and 65.13% control values at 350 mg/L, respectively. This strong antifungal activity suggests that 5-hydroxyl-5-methyl-2-hexenoic acid might be a promising candidate for new antifungal agents. PMID:20584599

Four copper(II) complexes have been prepared using macrocyclic ligands. The macrocyclic ligands have been synthesized by the condensation reaction of diethyl phthalate with Schiff bases derived from o-phenylene diamine and Knoevenagel condensed ?-ketoanilides (obtained by the condensation of acetoacetanilide and substituted benzaldehydes). The ligands and copper complexes have been characterized on the basis of Microanalytical, Mass, UV-Vis., IR and CV spectral studies, as well as conductivity data. On the basis of spectral studies, a square-planar geometry for the copper complexes has been proposed. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans. All the synthesized copper complexes showed stronger antifungal activities than free ligands. The minimum inhibitory concentrations (MIC) of the copper complexes were found in the range of 8~28 µg/ml. These compounds represent a novel class of metal-based antifungal agents which provide opportunities for a large number of synthetic variations for modulation of the activities. PMID:24039502

Novel copper(II) complexes have been synthesized from the macrocyclic Schiff bases derived from Knoevenagel condensed ?-ketoanilides (obtained by the condensation of acetoacetanilide and substituted benzaldehydes), 4-aminoantipyrine and o-phenylene diamine. The structural features have been determined from their analytical and spectral data. All the Cu(II) complexes exhibit square planar geometry. Their high molar conductance values support their 1: 2 electrolytic nature. The magnetic moment data provide evidence for the monomeric nature of the complexes. The X-band ESR spectra of the [CuL(1)](OAc)2 in DMSO solution at 300 and 77 K were recorded and their salient features are reported. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by well diffusion method. A comparative study of inhibition values of the Schiff bases and their complexes indicate that complexes exhibit higher antimicrobial activity than the Schiff bases. Copper ions proved to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. PMID:23983523

Cyclic voltammetric measurements were performed for Co(II), Ni(II), Cu(II) and Zn(II) complexes of 1: 1alternating copolymer, poly(3-nitrobenzylidene-1-naphthylamine-co-succinic anhydride) (L) and Ni(II) and Cu(II) complexes of 1: 1alternating copolymer, poly(3-nitrobenzylidene-1-naphthylamine-co-methacrylic acid) (L1). The in vitro biological screening effects of the investigated compounds were tested against the fungal species including Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans and bacterial species including Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa by well diffusion method. A comparative study of inhibition values of the copolymers and their complexes indicates that the complexes exhibit higher antimicrobial activity. Copper ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. The nuclease activity of the above metal complexes were assessed by gel electrophoresis assay and the results show that the copper complexes can cleave pUC18 DNA effectively in presence of hydrogen peroxide compared to other metal complexes. The degradation experiments using Rhodamine B dye indicate that the hydroxyl radical species are involved in the DNA cleavage reactions. PMID:23997637

Two Schiff base ligands L1and L2 were obtained by the condensation of glycylglycine respectively with imidazole-2-carboxaldehyde and indole-3-carboxaldehyde and their complexes with Zn(II) were prepared and characterized by microanalytical, conductivity measurement, IR, UV-Vis., XRD and SEM. The molar conductance measurement indicates that the Zn(II) complexes are 1: 1electrolytes. The IR data demonstrate the tetradentate binding of L1and tridentate binding of L2. The XRD data show that Zn(II) complexes with L1and L2 have the crystallite sizes of 53 and 61nm respectively. The surface morphology of the complexes was studied using SEM. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by the disc diffusion method. A comparative study of inhibition values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. Zinc ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. PMID:23990740

New N2O2 donor type Schiff base has been designed and synthesized by condensing acetoacetanilido-4-aminoantipyrine with 2-aminobenzoic acid in ethanol. Solid metal complexes of the Schiff base with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar conduction, fast atom bombardment (FAB) mass, IR, UV-Vis, and (1)H NMR spectral studies. The data show that the complexes have the composition of ML type. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, Candida albicans, Rhizoctonia bataicola and Trichoderma harizanum. All the metal complexes showed stronger antifungal activities than the free ligand. The minimum inhibitory concentrations (MIC) of the metal complexes were found in the range of 10~31 µg/ml. PMID:24015086

Two Schiff base ligands L1 and L2 were obtained by the condensation of glycylglycine respectively with imidazole-2-carboxaldehyde and indole-3-carboxaldehyde and their complexes with Zn(II) were prepared and characterized by microanalytical, conductivity measurement, IR, UV-Vis., XRD and SEM. The molar conductance measurement indicates that the Zn(II) complexes are 1 : 1 electrolytes. The IR data demonstrate the tetradentate binding of L1 and tridentate binding of L2. The XRD data show that Zn(II) complexes with L1 and L2 have the crystallite sizes of 53 and 61 nm respectively. The surface morphology of the complexes was studied using SEM. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by the disc diffusion method. A comparative study of inhibition values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. Zinc ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. PMID:23990740

Four copper(II) complexes have been prepared using macrocyclic ligands. The macrocyclic ligands have been synthesized by the condensation reaction of diethyl phthalate with Schiff bases derived from o-phenylene diamine and Knoevenagel condensed ?-ketoanilides (obtained by the condensation of acetoacetanilide and substituted benzaldehydes). The ligands and copper complexes have been characterized on the basis of Microanalytical, Mass, UV-Vis., IR and CV spectral studies, as well as conductivity data. On the basis of spectral studies, a square-planar geometry for the copper complexes has been proposed. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans. All the synthesized copper complexes showed stronger antifungal activities than free ligands. The minimum inhibitory concentrations (MIC) of the copper complexes were found in the range of 8~28 µg/ml. These compounds represent a novel class of metal-based antifungal agents which provide opportunities for a large number of synthetic variations for modulation of the activities. PMID:24039502

Novel copper(II) complexes have been synthesized from the macrocyclic Schiff bases derived from Knoevenagel condensed ?-ketoanilides (obtained by the condensation of acetoacetanilide and substituted benzaldehydes), 4-aminoantipyrine and o-phenylene diamine. The structural features have been determined from their analytical and spectral data. All the Cu(II) complexes exhibit square planar geometry. Their high molar conductance values support their 1 : 2 electrolytic nature. The magnetic moment data provide evidence for the monomeric nature of the complexes. The X-band ESR spectra of the [CuL1](OAc)2 in DMSO solution at 300 and 77 K were recorded and their salient features are reported. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by well diffusion method. A comparative study of inhibition values of the Schiff bases and their complexes indicate that complexes exhibit higher antimicrobial activity than the Schiff bases. Copper ions proved to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. PMID:23983523

New N2O2 donor type Schiff base has been designed and synthesized by condensing acetoacetanilido-4-aminoantipyrine with 2-aminobenzoic acid in ethanol. Solid metal complexes of the Schiff base with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar conduction, fast atom bombardment (FAB) mass, IR, UV-Vis, and 1H NMR spectral studies. The data show that the complexes have the composition of ML type. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, Candida albicans, Rhizoctonia bataicola and Trichoderma harizanum. All the metal complexes showed stronger antifungal activities than the free ligand. The minimum inhibitory concentrations (MIC) of the metal complexes were found in the range of 10~31 µg/ml. PMID:24015086

We hypothesized that apparently non-antagonistic soil bacteria may contribute to suppression of fungi during competitive interactions with other bacteria. Four soil bacteria (Brevundimonas sp., Luteibacter sp., Pedobacter sp. and Pseudomonas sp.) that exhibited little or no visible antifungal activity on different agar media were prescribed. Single and mixed strains of these species were tested for antagonism on a nutrient-poor agar medium against the plant pathogenic fungi Fusarium culmorum and Rhizoctonia solani and the saprotrophic fungus Trichoderma harzianum. Single bacterial strains caused little to moderate growth reduction of fungi (quantified as ergosterol), most probably due to nutrient withdrawal from the media. Growth reduction of fungi by the bacterial mixture was much stronger than that by the single strains. This appeared to be mostly due to competitive interactions between the Pseudomonas and Pedobacter strains. We argue that cohabitation of these strains triggered antibiotic production via interspecific interactions and that the growth reduction of fungi was a side-effect caused by the sensitivity of the fungi to bacterial secondary metabolites. Induction of gliding behavior in the Pedobacter strain by other strains was also observed. Our results indicate that apparently non-antagonistic soil bacteria may be important contributors to soil suppressiveness and fungistasis when in a community context. PMID:17233750

The lactase of the fungus Trametes versicolor was able to polymerize various halogen-, alkyl-, and alkoxy-substituted anilines, showing substrate specificity similar to that of horseradish peroxidase, whereas the lactase of Rhizoctonia praticola was active only with p-methoxyaniline. The substrate specificities of the enzymes were determined by using gas chromatography to measure the decrease in substrate concentration during incubation. With p-chloroaniline as the substrate, the peroxidase and the Trametes lactase showed maximum activity near pH 4.2. The transformation of this substrate gave rise to a number of oligomers, ranging from dimers to pentamers, as determined by mass spectrometry. The product profiles obtained by high-pressure liquid chromatography were similar for the two enzymes. A chemical reaction was observed between p-chloroaniline and an enzymatically formed dimer, resulting in the formation of a trimer. All three enzymes oxidized p-methoxyaniline to 2-amino-5-p-anisidinobenzoquinone di-p-methoxyphenylimine, but only the T. versicolor lactase and the peroxidase caused the formation of a pentamer (2,5-di-p-anisidinobenzoquinone di-p-methoxyphenylimine). These results demonstrate that in addition to horseradish peroxidase, a T. versicolor lactase can also polymerize aniline derivatives.

The cyanobacterium Nostoc strain ATCC 53789, a known cryptophycin producer, was tested for its potential as a source of natural pesticides. The antibacterial, antifungal, insecticidal, nematocidal, and cytotoxic activities of methanolic extracts of the cyanobacterium were evaluated. Among the target organisms, nine fungi (Armillaria sp., Fusarium oxysporum f. sp. melonis, Penicillium expansum, Phytophthora cambivora, P. cinnamomi, Rhizoctonia solani, Rosellinia, sp., Sclerotinia sclerotiorum, and Verticillium albo-atrum) were growth inhibited and one insect (Helicoverpa armigera) was killed by the extract, as well as the two model organisms for nematocidal (Caenorhabditis elegans) and cytotoxic (Artemia salina) activity. No antibacterial activity was detected. The antifungal activity against S. sclerotiorum was further studied with both extracts and biomass of the cyanobacterium in a system involving tomato as a host plant. Finally, the herbicidal activity of Nostoc strain ATCC 53789 was evaluated against a grass mixture. To fully exploit the potential of this cyanobacterium in agriculture as a source of pesticides, suitable application methods to overcome its toxicity toward plants and nontarget organisms must be developed. PMID:15184126

Biological control of plant pathogens is receiving increasing relevance, as compared to chemical methods, as they are eco-friendly, economical and indirectly improve plant quality and yield attributes. An investigation was undertaken to evaluate the potential of antagonistic cyanobacteria (Anabaena variabilis RPAN59 and A. oscillarioides RPAN69) fortified formulations for suppressing damping off disease in tomato seedlings challenged by the inoculation of a fungal consortium (Pythium debaryanum, Fusarium oxysporum lycopersici, Fusarium moniliforme and Rhizoctonia solani). Treatment with A. variabilis amended formulations recorded significantly higher plant growth parameters, than other treatments, including biological control (Trichoderma formulation) and chemical control (Thiram-Carbendazim). The A. variabilis amended compost-vermiculite and compost formulations exhibited 10-15 % lower disease severity and 40-50 % higher values than chemical and biological control treatments in terms of fresh weight and height of the plants. In future, in depth analyses regarding the mechanism involved in biocontrol by cyanobacteria and evaluation of these formulations under field conditions are proposed to be undertaken. PMID:22869418

Trichoderma species produce trichothecenes, most notably trichodermin and harzianum A (HA), by a biosynthetic pathway in which several of the involved proteins have significant differences in functionality compared to their Fusarium orthologues. In addition, the genes encoding these proteins show a genomic organization differing from that of the Fusarium tri clusters. Here we describe the isolation of Trichoderma arundinaceum IBT 40837 transformants which have a disrupted or silenced tri4 gene, a gene encoding a cytochrome P450 monooxygenase that oxygenates trichodiene to give rise to isotrichodiol, and the effect of tri4 gene disruption and silencing on the expression of other tri genes. Our results indicate that the tri4 gene disruption resulted in a reduced antifungal activity against Botrytis cinerea and Rhizoctonia solani and also in a reduced ability to induce the expression of tomato plant defense-related genes belonging to the salicylic acid (SA) and jasmonate (JA) pathways against B. cinerea, in comparison to the wild-type strain, indicating that HA plays an important function in the sensitization of Trichoderma-pretreated plants against this fungal pathogen. Additionally, the effect of the interaction of T. arundinaceum with B. cinerea or R. solani and with tomato seedlings on the expressions of the tri genes was studied. PMID:22562989

Four commercial composts were added to soil to study their effect on plant growth, total rhizosphere microflora, and incidence of plant growth-promoting rhizobacteria (PGPR) in the rhizosphere of tomato plants. Three of the compost treatments significantly improved plant growth, while one compost treatment significantly depressed it. Compost amendments caused only small variations in the total numbers of bacteria, actinomycetes, and fungi in the rhizosphere of tomato plants. A total of 709 bacteria were isolated from the four compost treatments and the soil control to determine the percentage of PGPR in each treatment. The PGPR tests measured antagonism to soilborne root pathogens, production of indoleacetic acid, cyanide, and siderophores, phosphate solubilization, and intrinsic resistance to antibiotics. Our results show that the addition of some composts to soil increased the incidence in the tomato rhizosphere of bacteria exhibiting antagonism towards Fusarium oxysporum f. sp. radicis-lycopersici, Pyrenochaeta lycopersici, Pythium ultimum, and Rhizoctonia solani. The antagonistic effects observed were associated with marked increases in the percentage of siderophore producers. No significant differences were observed in the percentage of cyanogens, whereas the percentages of phosphate solubilizers and indoleacetic acid producers were affected, respectively, by one and two compost treatments. Intrinsic resistance to antibiotics was only marginally different among the rhizobacterial populations. Our results suggest that compost may stimulate the proliferation of antagonists in the rhizosphere and confirm previous reports indicating that the use of composts in container media has the potential to protect plants from soilborne root pathogens. PMID:16534902

The ability of a polyphenoloxidase, the laccase of the fungus Rhizoctonia praticola, to detoxify phenolic pollutants was examined. The growth of the fungus could be inhibited by phenolic compounds, and the effective concentration was dependent on the substituents of the phenol. A toxic amount of a phenolic compound was added to a fungal growth medium in the presence or absence of a naturally occurring phenol, and half of the replicates also received laccase. The medium was then inoculated with R. praticola, and the levels of phenols in the medium were monitored by high-performance liquid chromatography analysis. The addition of the laccase reversed the inhibitory effect of 2,6-xylenol, 4-chloro-2-methylphenol, and p-cresol. Other compounds, e.g., o-cresol and 2,4-dichlorophenol, were detoxified only when laccase was used in conjunction with a natural phenol such as syringic acid. The toxicity of p-chlorophenol and 2,4,5-trichlorophenol could not be overcome by any additions. The ability of the laccase to alter the toxicity of the phenols appeared to be related to the capacity of the enzyme to decrease the levels of the parent compound by transformation or cross-coupling with another phenol. PMID:3223771

The antagonistic fungus Trichoderma harzianum is widely recognized as a potential biocontrol agent against several soil-borne plant pathogens. T. harzinum is rich source of chitinoltic enzymes. In vitro screening of 5 isolates of T. harzinum, one isolate of Chaetomium globosum and one isolate of Conetherium mentance, revealed that all of them had reduced growth area of Macrophomina phaseolina, Fusarium solaniand Rhizoctonia solani on PDA medium, significantly. The inhibition percentage ranged from 77.9 % to 55.9% for M. phaseolina and 59.2% to 40.4% for R. solani by T. harzinum and C. mentance, respectively. Inhibition for F. solani ranged from 76.5% to 55.7% by T. harzinum and C. globosum, respectively. Isozyme gel electrophoresis was used to assess chitinase activity secreted by selected isolates of T. harzinum under different pH degrees and temperatures. Obtained results indicated that activity of chitinase isozyme produced at 30 °C was higher than 15–20 °C for all tested isolates and activity of chitinase produced by isolates No. 4 and 5 of T. harzinum at pH (7–7.5) was higher than at pH 6, respectively. PMID:23961072

Bacteria associated with arbuscular mycorrhizal (AM) fungal spores may play functional roles in interactions between AM fungi, plant hosts and defence against plant pathogens. To study AM fungal spore-associated bacteria (AMB) with regard to diversity, source effects (AM fungal species, plant host) and antagonistic properties, we isolated AMB from surface-decontaminated spores of Glomus intraradices and Glomus mosseae extracted from field rhizospheres of Festuca ovina and Leucanthemum vulgare. Analysis of 385 AMB was carried out by fatty acid methyl ester (FAME) profile analysis, and some also identified using 16S rRNA gene sequence analysis. The AMB were tested for capacity to inhibit growth in vitro of Rhizoctonia solani and production of fluorescent siderophores. Half of the AMB isolates could be identified to species (similarity index 0.6) within 16 genera and 36 species. AMB were most abundant in the genera Arthrobacter and Pseudomonas and in a cluster of unidentified isolates related to Stenotrophomonas. The AMB composition was affected by AM fungal species and to some extent by plant species. The occurrence of antagonistic isolates depended on AM fungal species, but not plant host, and originated from G. intraradices spores. AM fungal spores appear to host certain sets of AMB, of which some can contribute to resistance by AM fungi against plant pathogens. PMID:18631178

The sugarcane root endophyte Trichoderma virens 223 holds enormous potential as a sustainable alternative to chemical pesticides in the control of sugarcane diseases. Its efficacy as a biocontrol agent is thought to be associated with its production of chitinase enzymes, including N-acetyl-ß-D-glucosaminidases, chitobiosidases and endochitinases. We used targeted gene deletion and RNA-dependent gene silencing strategies to disrupt N-acetyl-ß-D-glucosaminidase and endochitinase activities of the fungus, and to determine their roles in the biocontrol of soil-borne plant pathogens. The loss of N-acetyl-ß-D-glucosaminidase activities was dispensable for biocontrol of the plurivorous damping-off pathogens Rhizoctonia solani and Sclerotinia sclerotiorum, and of the sugarcane pathogen Ceratocystis paradoxa, the causal agent of pineapple disease. Similarly, suppression of endochitinase activities had no effect on R. solani and S. sclerotiorum disease control, but had a pronounced effect on the ability of T. virens 223 to control pineapple disease. Our work demonstrates a critical requirement for T. virens 223 endochitinase activity in the biocontrol of C. paradoxa sugarcane disease, but not for general antagonism of other soil pathogens. This may reflect its lifestyle as a sugarcane root endophyte. PMID:23110120

The effects of six species of phytopathogenic fungi mycelia as elicitors on trichodermin yield by Trichoderma brevicompactum were investigated. Neither nonviable nor viable mycelia of Botrytis cinerea, Alternaria solani, Colletotrichum lindemuthianum, and Thanatephorus cucumeris demonstrated any elicitation on the accumulation of trichodermin. However, the production of trichodermin was increased by the presence of viable/nonviable Rhizoctonia solani and Fusarium oxysporum mycelia. The strongest elicitation effect was found at the presence of nonviable R. solani. At the presence of nonviable R. solani, the maximum yield of trichodermin (144.55?mg/L) was significantly higher than the Control (67.8?mg/L), and the cultivation time to obtain the maximum yield of trichodermin decreased from 72?h to 60?h. No difference of trichodermin accumulation was observed by changing the concentration of nonviable R. solani from 0.1 to 1.6?g/L. It was observed that the optimum time for adding nonviable R. solani is immediately after inoculation. The diameter of T. brevicompactum mycelial globule after 72?h cultivation with nonviable R. solani elicitor was smaller than that of the Control. PMID:24385883

DNA sequence analysis of the internal transcribed spacer region 1 (ITS1) and random amplified polymorphic DNA (RAPD) markers were used to survey genetic variability in relation to agronomic and regional factors among 60 isolates of Thanatephorus cucumeris (anamorph Rhizoctonia solani) collected from lesions on potato stems or sclerotia of potato tubers. Based on comparative sequence analysis it was shown that all isolates belonged to anastomosis group 3 subgroup Potato Type (AG-3 PT). ITS1 sequence polymorphisms were found within 45 of the 60 isolates showing that different types of the ITS-region are present in individual isolates. Cloning and sequence analysis of the ITS1 region from three selected isolates with sequence polymorphism showed that two different ITS1-types were present in each isolate. RAPD analysis identified 51 RAPD-phenotypes among the 60 investigated isolates indicating a high level of diversity within the subgroup AG-3 PT. Putative clonal isolates with identical RAPD- and ITS1-types were identified within fields, and in one case the same phenotype was found in two different fields separated by several hundred kilometers. Population subdivision analysis based on phenotypic as well as genotypic diversities showed differentiation among populations from different fields when isolates were sampled from tubers, indicating restricted gene flow among soil populations. Low differentiation was seen among field populations sampled from stems, indicating that gene flow is taking place. The population structure was not influenced by the previous crop in the rotation nor by the two cultivars 'Sava' and 'Bintje'. PMID:15000234

Disease prevention is a current practice used to minimize fungal diseases of turfgrasses in lawns and golf greens. Prevention is accomplished through fungicide applications, and by periodic thatch removal. During the development of a microbial biodethatch product utilizing the lignocellulose-degrading Streptomyces hygroscopicus strains YCED9 and WYE53, we demonstrated using in vitro plate antagonism bioassays that both strains are antagonists of various turfgrass fungal pathogens. These activities were present when the cultures were growing on thatch, as demonstrated by antifungal antagonism bioassays with culture filtrates. Experiments conducted using a growth chamber demonstrated that a bio-dethatch formulation containing spores of strains YCED9 and WYE53 in a zeolite carrier, provided protection for Kentucky bluegrass seedlings against turfgrass pathogens, including Pythium ultimum, Fusarium oxysporum, Rhizoctonia solani, Sclerotinia homeocarpa, Gaeumannomyces graminis and Microdochium nivale. Results showed that by integrating the use of the S. hygroscopicus YCED9/WYE53 bio-dethatch formulation into routine turf management practices, it should be possible to both minimize thatch build-up while also controlling fungal turfgrass diseases by way of the antifungal biocontrol activity of these strains. This in turn would help control fungal pathogens in turfgrass while minimizing the need for routine chemical fungicide applications. PMID:10455494

Solanum tuberosum plants were transformed with three genetic constructions expressing the Nicotiana tabacum AP24 osmotine, Phyllomedusa sauvagii dermaseptin and Gallus gallus lysozyme, and with a double-transgene construction expressing the AP24 and lysozyme sequences. Re-transformation of dermaseptin-transformed plants with the AP24/lysozyme construction allowed selection of plants simultaneously expressing the three transgenes. Potato lines expressing individual transgenes or double- and triple-transgene combinations were assayed for resistance to Erwinia carotovora using whole-plant and tuber infection assays. Resistance levels for both infection tests compared consistently for most potato lines and allowed selection of highly resistant phenotypes. Higher resistance levels were found in lines carrying the dermaseptin and lysozyme sequences, indicating that theses proteins are the major contributors to antibacterial activity. Similar results were obtained in tuber infection tests conducted with Streptomyces scabies. Plant lines showing the higher resistance to bacterial infections were challenged with Phytophthora infestans, Rhizoctonia solani and Fusarium solani. Considerable levels of resistance to each of these pathogens were evidenced employing semi-quantitative tests based in detached-leaf inoculation, fungal growth inhibition and in vitro plant inoculation. On the basis of these results, we propose that stacking of these transgenes is a promising approach to achieve resistance to both bacterial and fungal pathogens. PMID:22115953

This work was aimed to produce lipopeptides by Bacillus amyloliquefaciens XZ-173 in solid state fermentation using agro-industrial byproducts. A central composite design was used to get the highest lipopeptides production. Results revealed that the optimal conditions for maximum lipopeptides production were 1.79% starch and 1.91% yeast extract by employing 5.58 g soybean flour and 3.67 g rice straw as the solid substrate with initial pH 7.5, moisture content 55% and a 10% inoculum level at 30°C for 2 days. Under these conditions, the experimental yield of lipopeptides reached 50.01 mg/gds, which was very close to the predicted value (49.91 mg/gds). At high concentration, the lipopeptides extracted from fermented substrates showed strong antibiotic activity against Rhizoctonia solani and Ralstonia solanacearum and certain emulsification but good emulsion stability. This is the first report on lipopeptides production that uses rice straw as a major substrate. PMID:22418084

The diversity of mycorrhizal fungi associated with an introduced weed-like South African orchid (Disa bracteata) and a disturbance-intolerant, widespread, native West Australian orchid (Pyrorchis nigricans) were compared by molecular identification of the fungi isolated from single pelotons. Molecular identification revealed both orchids were associated with fungi from diverse groups in the Rhizoctonia complex with worldwide distribution. Symbiotic germination assays confirmed the majority of fungi isolated from pelotons were mycorrhizal and a factorial experiment uncovered complex webs of compatibility between six terrestrial orchids and 12 fungi from Australia and South Africa. Two weed-like (disturbance-tolerant rapidly spreading) orchids - D. bracteata and the indigenous Australian Microtis media, had the broadest webs of mycorrhizal fungi. In contrast, other native orchids had relatively small webs of fungi (Diuris magnifica and Thelymitra crinita), or germinated exclusively with their own fungus (Caladenia falcata and Pterostylis sanguinea). Orchids, such as D. bracteata and M. media, which form relationships with diverse webs of fungi, had apparent specificity that decreased with time, as some fungi had brief encounters with orchids that supported protocorm formation but not subsequent seedling growth. The interactions between orchid mycorrhizal fungi and their hosts are discussed. PMID:17289365

After harvest, vegetables are often spoiled by a wide variety of microorganisms including many bacterial and fungal species. The most common bacterial agents are Erwinia carotovora, Pseudomonas spp., Corynebacterium, Xanthomonas campestris, and lactic acid bacteria with E. carotovora being the most common, attacking virtually every vegetable type. Fungi commonly causing spoilage of fresh vegetables are Botrytis cinerea, various species of the genera Alternaria, Aspergillus, Cladosporium, Colletotrichum, Phomopsis, Fusarium, Penicillium, Phoma, Phytophthora, Pythium and Rhizopus spp., Botrytis cinerea, Ceratocystis fimbriata, Rhizoctonia solani, Sclerotinia sclerotiorum, and some mildews. A few of these organisms show a substrate preference whereas others such as Botrytis cinerea, Colletotrichum, Alternaria, Cladosporium, Phytophthora, and Rhizopus spp., affect a wide variety of vegetables causing devastating losses. Many of these agents enter the plant tissue through mechanical or chilling injuries, or after the skin barrier has been broken down by other organisms. Besides causing huge economic losses, some fungal species could produce toxic metabolites in the affected sites, constituting a potential health hazard for humans. Additionally, vegetables have often served as vehicles for pathogenic bacteria, viruses, and parasites and were implicated in many food borne illness outbreaks. In order to slow down vegetable spoilage and minimize the associated adverse health effects, great caution should be taken to follow strict hygiene, good agricultural practices (GAPs) and good manufacturing practices (GMPs) during cultivation, harvest, storage, transport, and marketing. PMID:15839403

Background During rice blast fungal attack, plant xylanase inhibitor proteins (XIPs) that inhibit fungal xylanase activity are believed to act as a defensive barrier against fungal pathogens. To understand the role of XIPs in rice, a xylanase inhibitor was cloned from rice. The expression of this gene was examined at the transcriptional/translational levels during compatible and incompatible interactions, and the biochemical activity of this protein was also examined. Results Sequence alignment revealed that the deduced amino acid sequence of OsCLP shares a high degree of similarity with that of other plant TAXI-type XIPs. However, recombinant OsCLP did not display inhibitory activity against endo-1,4-?-xylanase enzymes from Aureobasidium pullulans (A. pullulans) or Trichoderma viride (T. viride). Instead, an in-gel activity assay revealed strong chitinase activity. The transcription and translation of OsCLP were highly induced when rice was exposed to pathogens in an incompatible interaction. In addition, exogenous treatment with OsCLP affected the growth of the basidiomycete fungus Rhizoctonia solani through degradation of the hyphal cell wall. These data suggest that OsCLP, which has chitinase activity, may play an important role in plant defenses against pathogens. Conclusions Taken together, our results demonstrate that OsCLP may have antifungal activity. This protein may directly inhibit pathogen growth by degrading fungal cell wall components through chitinase activity. PMID:23331415

Predictability of undesired events is a question of great interest in many scientific disciplines including seismology, economy and epidemiology. Here, we focus on the predictability of invasion of a broad class of epidemics caused by diseases that lead to permanent immunity of infected hosts after recovery or death. We approach the problem from the perspective of the science of complexity by proposing and testing several strategies for the estimation of important characteristics of epidemics, such as the probability of invasion. Our results suggest that parsimonious approximate methodologies may lead to the most reliable and robust predictions. The proposed methodologies are first applied to analysis of experimentally observed epidemics: invasion of the fungal plant pathogen Rhizoctonia solani in replicated host microcosms. We then consider numerical experiments of the susceptible–infected–removed model to investigate the performance of the proposed methods in further detail. The suggested framework can be used as a valuable tool for quick assessment of epidemic threat at the stage when epidemics only start developing. Moreover, our work amplifies the significance of the small-scale and finite-time microcosm realizations of epidemics revealing their predictive power. PMID:22513723

A bacterial strain designated as BPM3 isolated from mud of a natural hot water spring of Nambar Wild Life Sanctuary, Assam, India, strongly inhibited growth of phytopathogenic fungi (Fusarium oxysporum f. sp. ciceri, F. semitectum, Magnaporthe grisea and Rhizoctonia oryzae) and gram-positive bacterium (Staphylococcus aureus). The maximum growth and antagonistic activity was recorded at 30°C, pH 8.5 when starch and peptone were amended as carbon and nitrogen sources, respectively. In greenhouse experiment, this bacterium (BPM3) suppressed blast disease of rice by 30-67% and protected the weight loss by 35-56.5%. The maximum disease protection (67%) and weight loss protection (56.5%) were recorded when the bacterium was applied before 2 days of the pathogen inoculation. Antifungal and antibacterial compounds were isolated from the bacterium which also inhibited the growth of these targeted pathogens. The compounds were purified and on spectroscopic analysis of a purified fraction having R(f) 0.22 which showed strong antifungal and antibacterial activity indicated the presence of C-H, carbonyl group, dimethyl group, -CH(2) and methyl group. The bacterium was characterized by morphological, biochemical and molecular approaches and confirmed that the strain BPM3 is Brevibacillus laterosporus. PMID:20630733

The scarcity of fresh water in the Mediterranean region necessitates the search for halotolerant agents of biological control of plant diseases that can be applied in arid-zone agriculture irrigated with saline water. Among 29 Trichoderma strains previously isolated from Mediterranean Psammocinia sp. sponges, the greatest number of isolates belong to the Trichoderma longibrachiatum-Hypocrea orientalis species pair (9), H. atroviridis/T. atroviride (9), and T. harzianum species complex (7), all of which are known for high mycoparasitic potential. In addition, one isolate of T. asperelloides and two putative new species, Trichoderma sp. O.Y. 14707 and O.Y. 2407, from Longibrachiatum and Strictipilosa clades, respectively, have been identified. In vitro salinity assays showed that the ability to tolerate increasing osmotic pressure (halotolerance) is a strain- or clade-specific property rather than a feature of a species. Only a few isolates were found to be sensitive to increased salinity, while others either were halotolerant or even demonstrated improved growth in increasingly saline conditions. In vitro antibiosis assays revealed strong antagonistic activity toward phytopathogens due to the production of both soluble and volatile metabolites. Two marine-derived Trichoderma isolates, identified as T. atroviride and T. asperelloides, respectively, effectively reduced Rhizoctonia solani damping-off disease on beans and also induced defense responses in cucumber seedlings against Pseudomonas syringae pv. lachrimans. This is the first inclusive evaluation of marine fungi as potential biocontrol agents. PMID:21666030

Trichothecenes are sesquiterpenoid mycotoxins produced mainly by Fusarium species. Harzianum A (HA), a non-phytotoxic trichothecene produced by Trichoderma arundinaceum, has recently been found to have antagonistic activity against fungal plant pathogens and to induce plant genes involved in defense responses. In the present work, we have shown that disruption of the T. arundinaceum tri5 gene, which encodes a terpene synthase, stops the production of HA, alters the expression of other tri genes involved in HA biosynthesis, and alters the expression of hmgR, dpp1, erg9, erg1, and erg7, all genes involved in terpene biosynthetic pathways. An increase in the level of ergosterol biosynthesis was also observed in the tri5 disrupted transformant in comparison with the wild type strain. The loss of HA also resulted in a drastic reduction of the biocontrol activity of the transformants against the phytopathogenic fungi Botrytis cinerea and Rhizoctonia solani. Finally, the effect of tri5 gene disruption on the regulation and balance of intermediates in terpene biosynthetic pathways, as well as the hypothetical physiological role of trichothecenes, both inter- and intracellularly, on regulation and biocontrol, are discussed. PMID:23454546

Four commercial composts were added to soil to study their effect on plant growth, total rhizosphere microflora, and incidence of plant growth-promoting rhizobacteria (PGPR) in the rhizosphere of tomato plants. Three of the compost treatments significantly improved plant growth, while one compost treatment significantly depressed it. Compost amendments caused only small variations in the total numbers of bacteria, actinomycetes, and fungi in the rhizosphere of tomato plants. A total of 709 bacteria were isolated from the four compost treatments and the soil control to determine the percentage of PGPR in each treatment. The PGPR tests measured antagonism to soilborne root pathogens, production of indoleacetic acid, cyanide, and siderophores, phosphate solubilization, and intrinsic resistance to antibiotics. Our results show that the addition of some composts to soil increased the incidence in the tomato rhizosphere of bacteria exhibiting antagonism towards Fusarium oxysporum f. sp. radicis-lycopersici, Pyrenochaeta lycopersici, Pythium ultimum, and Rhizoctonia solani. The antagonistic effects observed were associated with marked increases in the percentage of siderophore producers. No significant differences were observed in the percentage of cyanogens, whereas the percentages of phosphate solubilizers and indoleacetic acid producers were affected, respectively, by one and two compost treatments. Intrinsic resistance to antibiotics was only marginally different among the rhizobacterial populations. Our results suggest that compost may stimulate the proliferation of antagonists in the rhizosphere and confirm previous reports indicating that the use of composts in container media has the potential to protect plants from soilborne root pathogens. PMID:16534902

In this study, antipathogenic activities of the twig essential oil and its constituents from Chamaecyparis formosensis Matsum were evaluated in vitro against six plant pathogenic fungi. The essential oil from the fresh twigs was isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. Twenty-five compounds were identified, representing 98.9% of the oil. The main components were beta-eudesmol (25.1%), tau-muurolol (21.6%), elemol (15.0%), totarol (14.9%), and alpha-cadinol (12.4%). The twig oil (500 mcirog/mL) showed growth inhibitory activity against the phytopathogenic fungi, Fusarium oxysporum, Pestalotiopsis funereal, and Ganoderma austral, with antifungal indices of 92.7%, 71.1%, and 87.7%, respectively. In addition, the oil suppressed totally the growth of Rhizoctonia solani, Colletotrichum gloeosporioides, and Fusarium solani. In order to ascertain the source compounds of these antipathogenic activities, the main components were individually evaluated. Tau-Muurolol and alpha-cadinol exhibited excellent activity against F. oxysporum, R. solani, C. gloeosporioides, and F. solani, with IC50 < 50 microg/mL. These compounds also efficiently inhibited the mycelial growths of P. funereal and G. austral. Thus, alpha-cadinol and tau-muurolol could be considered as potential natural fungicides for controlling fungal pathogens and worth. PMID:22908586

Presently, chemical seed treatments are in discussion due to their directly or indirectly impacts on human health or other living organisms. They may also negatively affect the ecosystem and the food chain. In rice seeds, chemicals may cause phytotoxic effects including seed degradation. Eugenol is the main component of clove (Eugenia caryophillis) oil, which was proved to act simultaneously as bactericide, virocide and especially fungicide. The in vitro study was aimed to compare the inhibitory effect of the following seed treatment substances against seed borne fungi and their shelf-life during 12 months of storage; conventional captan (CA), chitosan-lignosulphonate polymer (CL), eugenol incorporated into chitosan-lignosulphonate polymer (E+CL) and control (CO). The obtained results of fungi inhibition were classified in three groups, which showed at first that CA treatment led to a better, i.e., longer, inhibitory effect on Alternaria padwickii, Rhizoctonia solani, Curvularia sp., Aspergillus flavus and Aspergillus niger than E+CL. Secondly, E+CL coating polymer showed the longest inhibitory effect against Bipolaris oryzae and Nigrospora oryzae compared to CA and CL coating polymer. Finally, both CA and E+CL coating polymer had non-significant difference inhibitory effect on Fusarium moniliforme. The variant of CL coating polymer for seed coating was only during the first 6 months of storage able to inhibit all species of the observed seed borne fungi, whereas CA and E+CL coating polymer were capable to inhibit most of the fungi until 9 months of storage. PMID:19899320

A new alkalophilic low-molecular-mass chitinase of 14 kD from the potent biocontrol agent Bacillus subtilis JN032305 was partially purified and enzymology of the chitinase was studied. The enzyme showed optimal pH of 9.0 and temperature of 50°C. The enzyme was found stable during the 60-min incubation at 50 °C. The chitinase was inhibited by group specific agents like IAA, DAN, TLCK, and SDS and metal ions Mg(2+), Ca(2+), Fe(2+), Mn(2+), Ba(2+), and Hg(2+), whereas Zn(2+) did not show significant inhibitory effect against the chitinase. PMSF partially inhibited the enzyme. Substrates specificity tests indicated that the enzyme showed 75% of relative activity on glycol chitin, 58% on carboxymethylcellulose (CMC), 33% on chitin flakes, and 166% laminarin compared to that on colloidal chitin. The enzyme also hydrolyzed 4-methylumbelliferyl-N-acetyl-D-glucosaminide, indicating its chitobiase activity. The chitinase of this study has broad specificity, which could hydrolyze not only the glycosidic bond in GlcNAc-GlcNAc but also that of related carbohydrates with glycosidic linkages. The partially purified chitinase not only showed antifungal activity against Rhizoctonia solani and Colletotrichum gloeosporioides, two potent phytopathogens of chilli, but also increased the germination of chilli seeds when infected with the two potent phytopathogenic fungi. PMID:24499366

Plant growth-promoting fungi (PGPF) have the potential to confer several benefits to plants in terms of growth and protection against pests and pathogens. In the present study, we tested whether a PGPF isolate, Penicillium spp. GP15-1 (derived from zoysiagrass rhizospheres), stimulates growth and disease resistance in the cucumber plant. The use of the barley grain inoculum GP15-1 significantly enhanced root and shoot growth and biomass of cucumber plants. A root colonization study revealed that GP15-1 was a very rapid and efficient root colonizer and was isolated in significantly higher frequencies from the upper root parts than from the middle and lower root parts during the first 14 d of seedling growth. Inoculating the cucumber seedlings with GP15-1 significantly reduced the damping-off disease caused by Rhizoctonia solani, and the disease suppression effects of GP15-1 were considerably influenced by the inoculum potential of both GP15-1 and the pathogen. Treatment with the barley grain inoculum or a cell-free filtrate of GP15-1 increased systemic resistance against leaf infection by the anthracnose pathogen Colletotrichum orbiculare, resulting in a significant decrease in lesion number and size. Molecular and phylogenetic analyses of internal transcribed spacer sequences of the genomic DNA of GP15-1 revealed that the fungal isolate is a strain of either Penicillium neoechinulatum or Penicillium viridicatum. PMID:24671024

The endophytic fungus strain 0248, isolated from garlic, was identified as Trichoderma brevicompactum based on morphological characteristics and the nucleotide sequences of ITS1-5.8S- ITS2 and tef1. The bioactive compound T2 was isolated from the culture extracts of this fungus by bioactivity-guided fractionation and identified as 4?-acetoxy-12,13- epoxy-?(9)-trichothecene (trichodermin) by spectral analysis and mass spectrometry. Trichodermin has a marked inhibitory activity on Rhizoctonia solani, with an EC50 of 0.25 ?g mL(-1). Strong inhibition by trichodermin was also found for Botrytis cinerea, with an EC50 of 2.02 ?g mL(-1). However, a relatively poor inhibitory effect was observed for trichodermin against Colletotrichum lindemuthianum (EC50 = 25.60 ?g mL(-1)). Compared with the positive control Carbendazim, trichodermin showed a strong antifungal activity on the above phytopathogens. There is little known about endophytes from garlic. This paper studied in detail the identification of endophytic T. brevicompactum from garlic and the characterization of its active metabolite trichodermin. PMID:24948941

Antifungal resistance and toxicity problems of conventional fungicides highlighted the requirement of search for new safe antifungal agents. To comply with the requirement, we discovered four new non-cytotoxic lipopeptides, gageopeptides A-D, 1-4, from a marine-derived bacterium Bacillus subtilis. The structures and stereochemistry of gageopeptides were determined by NMR data analysis and chemical means. Gageopeptides exhibited significant antifungal activities against pathogenic fungi Rhizoctonia solani, Botrytis cinerea, and Colletotrichum acutatum with minimum inhibitory concentration (MIC) values of 0.02-0.06 ?M. In addition, these lipopeptides showed significant motility inhibition and lytic activities against zoospores of the late blight pathogen Phytophthora capsici. These compounds also showed potent antimicrobial activity against Gram positive and Gram negative bacteria with MIC values of 0.04-0.08 ?M. However, gageopeptides A-D did not exhibit any cytotoxicity (GI50 > 25 ?M) against cancer cell lines in sulforhodamine B (SRB), 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), and WST-1 ((4-[3-4-iodophenyl]-2-(4-nitrophenyl)-2H-5-tetrazolio)-1,3-benzene disulfonate)) assays, demonstrating that these compounds could be promising candidates for the development of non-cytotoxic antifungal agents. PMID:24857413

The endophytic fungus strain 0248, isolated from garlic, was identified as Trichoderma brevicompactum based on morphological characteristics and the nucleotide sequences of ITS1-5.8S- ITS2 and tef1. The bioactive compound T2 was isolated from the culture extracts of this fungus by bioactivity-guided fractionation and identified as 4?-acetoxy-12,13- epoxy-?9-trichothecene (trichodermin) by spectral analysis and mass spectrometry. Trichodermin has a marked inhibitory activity on Rhizoctonia solani, with an EC50 of 0.25 ?gmL?1. Strong inhibition by trichodermin was also found for Botrytis cinerea, with an EC50 of 2.02 ?gmL?1. However, a relatively poor inhibitory effect was observed for trichodermin against Colletotrichum lindemuthianum (EC50 = 25.60 ?gmL?1). Compared with the positive control Carbendazim, trichodermin showed a strong antifungal activity on the above phytopathogens. There is little known about endophytes from garlic. This paper studied in detail the identification of endophytic T. brevicompactum from garlic and the characterization of its active metabolite trichodermin. PMID:24948941

Few transition metal complexes of tetradentate N2O2 donor Schiff base ligands containing 2-hydroxybenzylidene-4-aminoantipyrine and amino acids (alanine/valine) abbreviated to KHL1/KHL2 have been synthesized. All the metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The Schiff bases KHL1/KHL2 are found to act as tetradentate ligands using N2O2 donor set of atoms leading to a square-planar geometry for the complexes around the metal ions. The binding behaviors of the complexes to calf thymus DNA have been investigated by absorption spectra, viscosity measurements and cyclic voltammetry. The DNA binding constants reveal that all these complexes interact with DNA through minor groove binding mode. The studies on mechanism of photocleavage reveal that singlet oxygen (1O2) and superoxide anion radical (O2rad -) may play an important role in the photocleavage. The Schiff bases and their metal complexes have been screened for their in vitro antibacterial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae and antifungal activities against Aspergillus niger, Fusarium solani, Culvularia lunata, Rhizoctonia bataicola and Candida albicans by MIC method.

A new Schiff base ligand (HL) was synthesized by the condensation reaction between 2'-methyleacetoacetanilide and 2-amino-3-hydroxypyridine. Its Co(II), Ni(II), Cu(II) and Zn(II) complexes were prepared by the interaction of the ligand with metal(II) chloride. They were characterized by elemental analysis, IR, 1H NMR, EPR, UV-Vis, magnetic susceptibility measurements, conductivity measurements and FAB-mass spectra. The interaction of the complexes with calf thymus DNA (CT-DNA) has been investigated by UV absorption, viscosity and cyclic voltammetry methods, and the mode of CT-DNA binding to the complexes has been explored. Furthermore, the DNA cleavage activity by the complexes was performed. It was found to be oxidative hydroxyl radical cleavage in the presence of 3-mercaptopropionic acid (MPA). The Schiff base and its complexes have been screened for their antibacterial ( Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa) and antifungal ( Aspergillus niger, Rhizopus stolonifer, Rhizoctonia bataicola and Candida albicans) activities and the data reveal that the complexes have higher activity than the free ligand.

Trichoderma species produce trichothecenes, most notably trichodermin and harzianum A (HA), by a biosynthetic pathway in which several of the involved proteins have significant differences in functionality compared to their Fusarium orthologues. In addition, the genes encoding these proteins show a genomic organization differing from that of the Fusarium tri clusters. Here we describe the isolation of Trichoderma arundinaceum IBT 40837 transformants which have a disrupted or silenced tri4 gene, a gene encoding a cytochrome P450 monooxygenase that oxygenates trichodiene to give rise to isotrichodiol, and the effect of tri4 gene disruption and silencing on the expression of other tri genes. Our results indicate that the tri4 gene disruption resulted in a reduced antifungal activity against Botrytis cinerea and Rhizoctonia solani and also in a reduced ability to induce the expression of tomato plant defense-related genes belonging to the salicylic acid (SA) and jasmonate (JA) pathways against B. cinerea, in comparison to the wild-type strain, indicating that HA plays an important function in the sensitization of Trichoderma-pretreated plants against this fungal pathogen. Additionally, the effect of the interaction of T. arundinaceum with B. cinerea or R. solani and with tomato seedlings on the expressions of the tri genes was studied. PMID:22562989

We studied the potential of the humus layer of the Norway spruce stands to supply beneficial rhizobacteria to birch (Betula pendula), alder (Alnus incana) and fescue grass (Festuca rubra), representatives of pioneer vegetation after clear-cutting of the coniferous forest. Axenically grown seedlings of these species were inoculated with the acid spruce humus, pH 3.7-5.3. Actinorhizal propagules, capable of nodulating alder, were present in high density (10(3) g(-1)) in humus of long-term limed plots, whereas plots with nitrogen fertilization contained almost none (=10 g(-1)). The genera most frequently found in the humus were Bacillus, Paenibacillus, Arthrobacter, Nocardia, Rhodococcus and Pseudomonas, independently of prior liming or fertilization of the plots. The taxa found in the seedling roots differed from that in humus by the prevalence of the Gram-negative genera Pseudomonas, Alcaligenes and Comamonas. Enrichment cultures of the roots on nitrogen-free media yielded Paenibacillus and Rhodococcus species. Nitrogen-fixing R. erythropolis and a novel Paenibacillus, closest by full sequence of 16S rDNA to P. durus, represented new classes of nitrogen-fixing rhizosphere bacteria. In addition, nitrogen-fixing R. fascians was found in the humus. The rhizoflora and humus contained high proportions of bacteria antagonistic towards plant pathogenic Rhizoctonia sp., Botrytis cinerea and Fusarium culmorum. The antagonistic isolates also commonly produced siderophores and/or cell wall degrading enzymes. PMID:10640667

A series of benzofurazan derivatives were prepared and evaluated for their biological activities against four important phytopathogenic fungi, namely, Rhizoctonia solani, Sclerotinia sclerotiorum, Fusarium graminearum and Phytophthora capsici, using the mycelium growth inhibition method. The structures of these compounds were characterized by (1)H NMR, (13)C NMR, and HRMS. N-(3-chloro-4-fluorophenyl)-7-nitrobenzo[c][1,2,5]oxadiazol-4-amine (A3) displayed the maximum antifungal activity against R. solani (IC50 = 1.91 ?g/mL), which is close to that of the positive control Carbendazim (IC50 = 1.42 ?g/mL). For other benzofurazan derivatives with nitro group at R(4) position (A series), 9 out of 30 compounds exhibited high antifungal effect against strain R. solani, with IC50 values less than 5 ?g/mL. Most of the derivatives with substituents at R(2) and R(3) positions (B series) displayed moderate growth inhibition against S. sclerotiorum (IC50 < 25 ?g/mL). Also, several benzofuran derivatives with nitro group at R(4) position and another conjugated aromatic ring at the R(1) position of the phenyl ring displayed high antifungal capability against strain R. solani. Compounds with substituents at R(2) and R(3) position had moderate efficacy against strain S. sclerotiorum. PMID:24813881

Few transition metal complexes of tetradentate N(2)O(2) donor Schiff base ligands containing 2-hydroxybenzylidene-4-aminoantipyrine and amino acids (alanine/valine) abbreviated to KHL(1)/KHL(2) have been synthesized. All the metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The Schiff bases KHL(1)/KHL(2) are found to act as tetradentate ligands using N(2)O(2) donor set of atoms leading to a square-planar geometry for the complexes around the metal ions. The binding behaviors of the complexes to calf thymus DNA have been investigated by absorption spectra, viscosity measurements and cyclic voltammetry. The DNA binding constants reveal that all these complexes interact with DNA through minor groove binding mode. The studies on mechanism of photocleavage reveal that singlet oxygen ((1)O(2)) and superoxide anion radical (O(2)(-)) may play an important role in the photocleavage. The Schiff bases and their metal complexes have been screened for their in vitro antibacterial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae and antifungal activities against Aspergillus niger, Fusarium solani, Culvularia lunata, Rhizoctonia bataicola and Candida albicans by MIC method. PMID:22885083

The fungus Rhizoctonia solani Kuhn is a widespread and destructive plant pathogen with a very broad host range. Although various pathogens, including R. solani, have been traditionally controlled using chemical pesticides, their use faces drawbacks such as environmental pollution, development of pesticide resistance, and other negative effects. Carbendazim is a well-known antifungal agent capable of controlling a broad range of plant diseases, but its use is hampered by its poor aqueous solubility. In this study, we describe an environmentally friendly pharmaceutical microemulsion system using carbendazim as the active ingredient, chloroform and acetic acid as solvents, and the surfactants HSH and 0204 as emulsifiers. This system increased the solubility of carbendazim to 30 g/L. The optimal microemulsion formulation was determined based on a pseudo-ternary phase diagram; its physicochemical characteristics were also tested. The cloud point was greater than 90°C and it was resistant to freezing down to ?18°C, both of which are improvements over the temperature range in which pure carbendazim can be used. This microemulsion meets the standard for pesticide microemulsions and demonstrated better activity against R. solani AG1-IA, relative to an aqueous solution of pure carbendazim (0.2 g/L). The mechanism of activity was reflected in the inhibition of against R. solani AG1-IA including mycelium growth, and sclerotia formation and germination were significantly better than that of 0.2 g/L carbendazim water solution according to the results of t-test done by SPSS 19. PMID:25310219

A total of 132 actinomycetes was isolated from different rice rhizosphere soils of Tamil Nadu, India, among which 57 showed antagonistic activity towards Rhizoctonia solani, which is sheath blight (ShB) pathogen of rice and other fungal pathogens such as Macrophomina phaseolina, Fusarium oxysporum, Fusarium udum and Alternaria alternata with a variable zone of inhibition. Potential actinomycete strain VSMGT1014 was identified as Streptomyces aurantiogriseus VSMGT1014 based on the morphological, physiological, biochemical and 16S rRNA sequence analysis. The strain VSMGT1014 produced lytic enzymes, secondary metabolites, siderophore, volatile substance and indole acetic acid. Crude metabolites of VSMGT1014 showed activity against R. solani at 5 µg ml(-1); however, the prominent inhibition zone was observed from 40 to 100 µg ml(-1). Reduced lesion heights observed in culture, cells-free filtrate, crude metabolites and carbendazim on challenge with pathogen in the detached leaf assay. The high content screening test clearly indicated denucleation of R. solani at 5 µg ml(-1) treatment of crude metabolite and carbendazim respectively. The results conclude that strain VSMGT1014 was found to be a potential candidate for the control of ShB of rice as a bio fungicide. PMID:25304022

The aim of the present study was to evaluate different biological activities of the fungus Chaetomium globosum (family Chaetomiaceae). The evaluation was done through testing its antimicrobial, antioxidant and anticancer effects. C. globosum was isolated from the Cucumber soil (rhizosphere) and caused inhibition of the mycelial growth of Fusarium solani, Rhizoctonia solani and Sclerotium rolfsii in the biculture test. Petroleum ether and ethyl acetate extracts of the liquid culture of C. globosum showed potent in vitro antioxidant activity. C. globosum proved potent antibacterial activity against Bacillus subtilis, Escherichia coli and Pseudomonas fluorescens. It also recorded significant antifungal activity against Candida albicans, F. solani, Fusarium oxysporum, R. solani and Pythium ultimum. It exerted cytotoxic effect on human hepatocellular carcinoma cell line (HepG2). Unsaponifiable and saponifiable matters of the petroleum ether extract showed the presence of hydrocarbons, sterols and fatty acids. The ethyl acetate extract showed the presence of prenisatin, chrysophanol, chrysazin, chaetoviridin A and B. The isolated secondary metabolites proved significant antioxidant and antimicrobial activity on B. subtilis, E. coli and R. solani. In conclusion, this fungus showed different biological activities. Further studies must be done to apply its use in the agricultural and medicinal field. PMID:24361402

Differences between endophytic and ectophytic bacterial communities with stress on antagonistic bacteria, were studied by comparing the composition of communities isolated from the rhizosphere, phyllosphere, endorhiza and endosphere of field-grown potato plants using a multiphasic approach. Terminal restriction fragment length polymorphism analysis of 16S rDNA of the bacterial communities revealed discrete microenvironment-specific patterns. To measure the antagonistic potential of potato-associated bacteria, a total of 2648 bacteria were screened by dual testing of antagonism to the soilborne pathogens Verticillium dahliae and Rhizoctonia solani. Composition and diversity of bacterial antagonists were mainly specific for each microenvironment. The rhizosphere and endorhiza were the main reservoirs for antagonistic bacteria and showed the highest similarity in their colonisation by antagonists. The most prominent species of all microenvironments was Pseudomonas putida, and rep-PCR with BOX primers showed that these isolates showed microenvironment-specific DNA fingerprints. P. putida isolates from the rhizosphere and endorhiza gave nearly identical fingerprints confirming the high similarity of bacterial populations. The phlD gene, involved in the production of the antibiotic 2,4-diacetyl-phloroglucinol, was found only among Pseudomonas isolates from the rhizosphere and endorhiza. Evaluation of the bacterial isolates for biocontrol potential based on fungal antagonism and physiological characteristics resulted in the selection of five promising isolates from each microenvironment. The most effective isolate was Serratia plymuthica 3Re4-18 isolated from the endorhiza. PMID:16329870

Detection, identification and quantification of plant pathogens are the cornerstones of preventive plant disease management. To detect multiple pathogens in a single assay, DNA array technology currently is the most suitable technique. However, for sensitive detection, polymerase chain reaction (PCR) amplification before array hybridization is required. To evaluate whether DNA array technology can be used to simultaneously detect and quantify multiple pathogens, a DNA macroarray was designed and optimized for accurate quantification over at least three orders of magnitude of the economically important vascular wilt pathogens Verticillium albo-atrum and Verticillium dahliae. A strong correlation was observed between hybridization signals and pathogen concentrations for standard DNA added to DNA from different origins and for infested samples. While accounting for specific criteria like amount of immobilized detector oligonucleotide and controls for PCR kinetics, accurate quantification of pathogens was achieved in concentration ranges typically encountered in horticultural practice. Subsequently, quantitative assessment of other tomato pathogens (Fusarium oxysporum, Fusarium solani, Pythium ultimum and Rhizoctonia solani) in environmental samples was performed using DNA array technology and correlated to measurements obtained using real-time PCR. As both methods of quantification showed a very high degree of correlation, the reliability and robustness of the DNA array technology is shown. PMID:16232285

The Bacillus subtilis strain NCD-2 is an important biocontrol agent against cotton verticillium wilt and cotton sore shin in the field, which are caused by Verticillium dahliae Kleb and Rhizoctonia solani Kuhn, respectively. A mutant of strain NCD-2, designated M216, with decreased antagonism to V. dahliae and R. solani, was selected by mini-Tn10 mutagenesis and in vitro virulence screening. The inserted gene in the mutant was cloned and identified as the phoR gene, which encodes a sensor kinase in the PhoP/PhoR two-component system. Compared to the wild-type strain, the APase activities of the mutant was decreased significantly when cultured in low phosphate medium, but no obvious difference was observed when cultured in high phosphate medium. The mutant also grew more slowly on organic phosphate agar and lost its phosphatidylcholine-solubilizing ability. The suppression of cotton seedling damping-off in vivo and colonization of the rhizosphere of cotton also decreased in the mutant strain when compared with the wild type strain. All of these characteristics could be partially restored by complementation of the phoR gene in the M216 mutant. PMID:21637491

The effects of six species of phytopathogenic fungi mycelia as elicitors on trichodermin yield by Trichoderma brevicompactum were investigated. Neither nonviable nor viable mycelia of Botrytis cinerea, Alternaria solani, Colletotrichum lindemuthianum, and Thanatephorus cucumeris demonstrated any elicitation on the accumulation of trichodermin. However, the production of trichodermin was increased by the presence of viable/nonviable Rhizoctonia solani and Fusarium oxysporum mycelia. The strongest elicitation effect was found at the presence of nonviable R. solani. At the presence of nonviable R. solani, the maximum yield of trichodermin (144.55?mg/L) was significantly higher than the Control (67.8?mg/L), and the cultivation time to obtain the maximum yield of trichodermin decreased from 72?h to 60?h. No difference of trichodermin accumulation was observed by changing the concentration of nonviable R. solani from 0.1 to 1.6?g/L. It was observed that the optimum time for adding nonviable R. solani is immediately after inoculation. The diameter of T. brevicompactum mycelial globule after 72?h cultivation with nonviable R. solani elicitor was smaller than that of the Control. PMID:24385883

Ribosome-inactivating proteins (RIPs) are enzymes that cleave a specific adenine base from the highly conserved sarcin/ricin (S/R) loop of the large ribosomal RNA, thus arresting protein synthesis at the translocation step. In the present study, we employed three RIPs to dissect the antifungal activity of RIPs as plant defense proteins. We measured the catalytic activity of RAT (the catalytic A-chain of ricin from Ricinus communis L.), saporin-S6 (from Saponaria officinalis L.), and ME (RIP from Mirabilis expansa R&P) against intact ribosomal substrates isolated from various pathogenic fungi. We further determined the enzymatic specificity of these three RIPs against fungal ribosomes, from Rhizoctonia solani Kuhn, Alternaria solani Sorauer, Trichoderma reesei Simmons and Candida albicans Berkhout, and correlated the data with antifungal activity. RAT showed the strongest toxicity against all tested fungal ribosomes, except for the ribosomes isolated from C. albicans, which were most susceptible to saporin. RAT and saporin showed higher enzymatic activity than ME against ribosomes from all of the fungal species assayed, but did not show detectable antifungal activity. In contrast, ME showed substantial inhibitory activity against fungal growth. Using N-hydroxysuccinimide-fluorescein labeling of RIPs and fluorescence microscopy, we determined that ME was targeted to the surface of fungal cells and transferred into the cells. Thus, ME caused ribosome depurination and subsequent fungal mortality. In contrast, saporin did not interact with fungal cells, correlating with its lack of antifungal activity. PMID:12447536

Nematode (Heterodera schachtii) resistance in sugar beet (Beta vulgaris) is controlled by a single dominant resistance gene, Hs1(pro-1). BvGLP-1 was cloned from resistant sugar beet. The BvGLP-1 messenger (m)RNA is highly upregulated in the resistant plants after nematode infection, suggesting its role in the Hs1(pro-1) mediated resistance. BvGLP-1 exhibits sequence homology to a set of plant germin-like proteins (GLP), from which several have proved to be functional in plant basal or defense resistance against fungal pathogens. To test whether BvGLP-1 is also involved in the plant-fungus interaction, we transferred BvGLP-1 into Arabidopsis and challenged the transgenic plants with the pathogenic fungi Verticillium longisporum and Rhizoctonia solani as well as with the beneficial endophytic fungus Piriformospora indica. The expression of BvGLP-1 in Arabidopsis elevated the H(2)O(2) content and conferred significant resistance to V. longisporum and R. solani but did not affect the beneficial interaction with P. indica in seedlings. Microscopic observations revealed a dramatic reduction in the amount of hyphae of the pathogenic fungi on the root surface as well as of fungal mycelium developed inside the roots of transgenic Arabidopsis compared with wild-type plants. Molecular analysis demonstrated that the BvGLP-1 expression in Arabidopsis constitutively activates the expression of a subset of plant defense-related proteins such as PR-1 to PR-4 and PDF1.2 but not PDF2.1 and PDF2.3. In contrast, the PDF2.1 mRNA level was downregulated. These data suggest an important role of BvGLP-1 in establishment of plant defense responses, which follow specific signaling routes that diverge from those induced by the beneficial fungus. PMID:20192832

ABSTRACT The interaction between the oomycete Pythium oligandrum and various soilborne oomycete and fungal plant pathogens (P. ultimum, P. aphanidermatum, Fusarium oxysporum f. sp. radicis-lycopersici, Verticillium albo-atrum, Rhizoctonia solani, and Phytophthora megasperma) was studied by light and electron microscopy in order to assess the relative contribution of mycoparasitism and antibiosis in the antagonistic process. Scanning electron microscope investigations of the interaction regions showed that structural alterations of all pathogenic fungi and oomycetes (except for Phytophthora megasperma) occurred soon after contact with the antagonist. Light and transmission electron microscope studies of the interaction region between the antagonist and P. ultimum revealed that intimate contact between both partners preceded a sequence of degradation events including aggregation of host cytoplasm and penetration of altered host hyphae. Localization of the host wall cellulose component showed that cellulose was altered at potential penetration sites. A similar scheme of events was observed during the interaction between P. oligandrum and F. oxysporum f. sp. radicis-lycopersici, with the exception that complete loss of host protoplasm was associated with antagonist invasion. The interaction between P. oligandrum and R. solani resulted in an abnormal deposition of a wall-like material at potential penetration sites for the antagonist. However, the antagonist displayed the ability to circumvent this barrier and penetrate host hyphae by locally altering the chitin component of the host hyphal wall. Interestingly, antagonist cells also showed extensive alteration as evidenced by the frequent occurrence of empty hyphal shells. In the case of Phytophthora megasperma, hyphal interactions did not occur, but hyphae of the plant pathogen were damaged severely. At least two distinct mechanisms appear to be involved in the process of oomycete and fungal attack by P. oligandrum: (i) mycoparasitism, mediated by intimate hyphal interactions, and (ii) antibiosis, with alteration of the host hyphae prior to contact with the antagonist. However, the possibility that the antagonistic process may rely on the dual action of antibiotics and hydrolytic enzymes is discussed. PMID:18944723

Cymbidium hybridum is one of the most popular pot orchids and cut flowers worldwide. However, the long vegetative growth period and the discordant blooming retarded its mass production. The mixotrophic nutritional mode of some chlorophyllous Cymbidium suggested the essential role of mycorrhizal fungi in the growth of adult green orchids. Here 34 root-associated endophytes were obtained from wild and cultivated Cymbidium and eight strains exhibited obvious growth-promoting effects on the C. hybridum plantlets with increasing root number, root diameter or new bud initiation. Among these, three isolates CL01, ZH3A-3 and CY5-1 with distinct cultural traits and colonization patterns showed better growth-promoting effects. Internal transcribed spacer sequence analyses and morphological observation revealed isolate CL01 belonged to Tulasnella-like Rhizoctonia, ZH3A-3, Umbelopsis nana and CY5-1, Scytalidium lignicola. Microscopic study showed isolate CL01 formed typical orchid mycorrhiza and isolate CY5-1 formed pseudo-mycorrhiza with orchid, whereas hyphae of isolate ZH3A-3 aggregated in the host velamen cells at regular intervals and caused the hypertrophied nucleus and aggregated cytoplasm of neighboring host cell. These three isolates significantly enhanced the increased percentage of total fresh weight of plantlets compared with un-inoculated control (83, 99 and 75%, respectively). In addition, isolate CL01 increased the N, P, Zn, Cu, Fe contents and ZH3A-3 significantly improved K, Ca, Cu, Mn contents of the symbiotic plantlets compared with control. These results suggested that the mass production of C. hybridum and related orchids could be improved by different beneficial fungi from its parents. PMID:24532077

A novel endophyte designated Collophora aceris, was obtained from stem tissues of Douglas Maple (Acer glabrum var. douglasii) in a Pacific Northwest temperate rainforest. Colonies were slow growing, white, creamy, moist, and translucent to opaque on potato dextrose agar and other media with few aerial hyphae. It also produced solid, dark sclerotia (200-400 ?m) on oatmeal agar and no evidence of pseudopycnidia as per other Collophora spp. Conidia were rod-like in the size ranging from 2.2-8.4?×?0.8-1.8 ?m and produced holoblastically on conidiogenous cells by budding with no collarette at the budding site. Phylogenetic analyses, based on 18S rDNA sequence data, showed that C. aceris possessed 99 % similarity to other Collophora spp. However, ITS-5.8S rDNA sequence data indicated that the organism was potentially related to Allantophomopsis spp. Finally, combined morphological, physiological, and molecular genetics data indicated that this organism is most like Collophora spp. but it is distinctly unique when compared to all other fungi in this group. It is to be noted that this is the first report of any member of this genus existing as an endophyte. This fungus makes a wide spectrum antimycotic agent (Collophorin) with biological activity against such pathogenic fungi as Pythium ultimum, Phytophthora cinnamomi, Phytophthora palmivora, and Rhizoctonia solani. Collophorin was purified to homogeneity and shown to have a unique mass of 120.0639, an empirical formula of C8H8O1, and UV absorption bands at 260 and 378 nm. This work also indicates that C. aceris possesses the biological potential to provide protection of its host against an array of common plant pathogens. PMID:23996143

Sheath blight (ShB) caused by the soil-borne pathogen Rhizoctonia solani is one of the most devastating diseases in rice world-wide. Global attention has focused on examining individual mapping populations for quantitative trait loci (QTLs) for ShB resistance, but to date no study has taken advantage of association mapping to examine hundreds of lines for potentially novel QTLs. Our objective was to identify ShB QTLs via association mapping in rice using 217 sub-core entries from the USDA rice core collection, which were phenotyped with a micro-chamber screening method and genotyped with 155 genome-wide markers. Structure analysis divided the mapping panel into five groups, and model comparison revealed that PCA5 with genomic control was the best model for association mapping of ShB. Ten marker loci on seven chromosomes were significantly associated with response to the ShB pathogen. Among multiple alleles in each identified loci, the allele contributing the greatest effect to ShB resistance was named the putative resistant allele. Among 217 entries, entry GSOR 310389 contained the most putative resistant alleles, eight out of ten. The number of putative resistant alleles presented in an entry was highly and significantly correlated with the decrease of ShB rating (r?=?-0.535) or the increase of ShB resistance. Majority of the resistant entries that contained a large number of the putative resistant alleles belonged to indica, which is consistent with a general observation that most ShB resistant accessions are of indica origin. These findings demonstrate the potential to improve breeding efficiency by using marker-assisted selection to pyramid putative resistant alleles from various loci in a cultivar for enhanced ShB resistance in rice. PMID:22427867

Cynanchum komarovii Al Iljinski is a desert plant that has been used as analgesic, anthelminthic, and antidiarrheal, but also as herbal medicine to treat cholecystitis in people. In this work, an antifungal protein with sequence homology to chitinase was isolated from C. komarovii seeds and named CkChn134. The three-dimensional structure prediction of CkChn134 indicated that the protein has a loop domain formed a thin cleft, which is able to bind molecules and substrates. The protein and CkTLP synergistically inhibited the fungal growth of Verticillium dahliae, Fusarium oxysporum, Rhizoctonia solani, Botrytis cinerea, and Valsa mali in vitro. The full-length cDNA was cloned by RT-PCR and RACE-PCR according to the partial protein sequences obtained by nanoESI-MS/MS. The real-time PCR showed that the transcription level of CkChn134 had a significant increase under the stress of ethylene, NaCl, low temperature, drought, and pathogen infection, which indicates that CkChn134 may play an important role in response to abiotic and biotic stresses. The CkChn134 protein was located in the extracellular space/cell wall by CkChn134::GFP fusion protein in transgenic Arabidopsis. Furthermore, overexpression of CkChn134 significantly enhanced the resistance of transgenic Arabidopsis against V. dahliae. Interestingly, the coexpression of CkChn134 and CkTLP showed substantially greater protection against the fungal pathogen V. dahliae than either transgene alone. The results suggest that the CkChn134 is a good candidate protein or gene, and it had a potential synergistic effect with CkTLP for contributing to the development of disease-resistant crops. PMID:22532259

BACKGROUND: Combating the action of plant pathogenic microorganisms by mycoparasitic fungi has been announced as an attractive biological alternative to the use of chemical fungicides since two decades. The fungal genus Trichoderma includes a high number of taxa which are able to recognize, combat and finally besiege and kill their prey. Only fragments of the biochemical processes related to this ability have been uncovered so far, however. RESULTS: We analyzed genome-wide gene expression changes during the begin of physical contact between Trichoderma atroviride and two plant pathogens Botrytis cinerea and Rhizoctonia solani, and compared with gene expression patterns of mycelial and conidiating cultures, respectively. About 3000 ESTs, representing about 900 genes, were obtained from each of these three growth conditions. 66 genes, represented by 442 ESTs, were specifically and significantly overexpressed during onset of mycoparasitism, and the expression of a subset thereof was verified by expression analysis. The upregulated genes comprised 18 KOG groups, but were most abundant from the groups representing posttranslational processing, and amino acid metabolism, and included components of the stress response, reaction to nitrogen shortage, signal transduction and lipid catabolism. Metabolic network analysis confirmed the upregulation of the genes for amino acid biosynthesis and of those involved in the catabolism of lipids and aminosugars. CONCLUSION: The analysis of the genes overexpressed during the onset of mycoparasitism in T. atroviride has revealed that the fungus reacts to this condition with several previously undetected physiological reactions. These data enable a new and more comprehensive interpretation of the physiology of mycoparasitism, and will aid in the selection of traits for improvement of biocontrol strains by recombinant techniques.

Pseudomonas fluorescens 2P24 is a soilborne bacterium that synthesizes and excretes multiple antimicrobial metabolites. The polyketide compound 2,4-diacetylphloroglucinol (2,4-DAPG), synthesized by the phlACBD locus, is its major biocontrol determinant. This study investigated two mutants defective in antagonistic activity against Rhizoctonia solani. Deletion of the gidA (PM701) or trmE (PM702) gene from strain 2P24 completely inhibited the production of 2,4-DAPG and its precursors, monoacetylphloroglucinol (MAPG) and phloroglucinol (PG). The transcription of the phlA gene was not affected, but the translation of the phlA and phlD genes was reduced significantly. Two components of the Gac/Rsm pathway, RsmA and RsmE, were found to be regulated by gidA and trmE, whereas the other components, RsmX, RsmY, and RsmZ, were not. The regulation of 2,4-DAPG production by gidA and trmE, however, was independent of the Gac/Rsm pathway. Both the gidA and trmE mutants were unable to produce PG but could convert PG to MAPG and MAPG to 2,4-DAPG. Overexpression of PhlD in the gidA and trmE mutants could restore the production of PG and 2,4-DAPG. Taken together, these findings suggest that GidA and TrmE are positive regulatory elements that influence the biosynthesis of 2,4-DAPG posttranscriptionally. PMID:24747907

Rice (Oryza sativa L.) is, on a global scale, one of the most important food crops. Although endophytic fungi and bacteria associated with rice have been investigated, little is known about the endophytic fungi of wild rice (Oryza granulate) in China. Here we studied the root endophytic mycobiota residing in roots of O. granulate by the use of an integrated approach consisting of microscopy, cultivation, ecological indices, and direct PCR. Microscopy confirmed the ubiquitousness of dark septate endophytes (DSEs) and sclerotium-like structures in root tissues. Isolations from 204 root segments from 15 wild rice plants yielded 58 isolates, for which 31 internal transcribed spacer (ITS)-based genotypes were recorded. The best BLAST match indicated that 34.5% of all taxa encountered may represent hitherto undescribed species. Most of the fungi were isolated with a very low frequency. Calculation of ecological indices and estimation of taxon accumulation curves indicated a high diversity of fungal species. A culture-independent approach was also performed to analyze the endophytic fungal community. Three individual clone libraries were constructed. Using a threshold of 90% similarity, 35 potentially different sequences (phylotypes) were found among 186 positive clones. Phylogenetic analysis showed that frequently detected clones were classified as Basidiomycota, and 60.2% of total analyzed clones were affiliated with unknown taxa. Exophiala, Cladophialophora, Harpophora, Periconia macrospinosa, and the Ceratobasidium/Rhizoctonia complex may act as potential DSE groups. A comparison of the fungal communities characterized by the two approaches demonstrated distinctive fungal groups, and only a few taxa overlapped. Our findings indicate a complex and rich endophytic fungal consortium in wild rice roots, thus offering a potential bioresource for establishing a novel model of plant-fungal mutualistic interactions. PMID:20038691

Application of the plant associated bacterium Bacillus amyloliquefaciens FZB42 on lettuce (Lactuca sativa) confirmed its capability to promote plant growth and health by reducing disease severity (DS) caused by the phytopathogenic fungus Rhizoctonia solani. Therefore this strain is commercially applied as an eco-friendly plant protective agent. It is able to produce cyclic lipopeptides (CLP) and polyketides featuring antifungal and antibacterial properties. Production of these secondary metabolites led to the question of a possible impact of strain FZB42 on the composition of microbial rhizosphere communities after its application. Rating of DS and lettuce growth during a field trial confirmed the positive impact of strain FZB42 on the health of the host plant. To verify B. amyloliquefaciens as an environmentally compatible plant protective agent, its effect on the indigenous rhizosphere community was analyzed by metagenome sequencing. Rhizosphere microbial communities of lettuce treated with B. amyloliquefaciens FZB42 and non-treated plants were profiled by high-throughput metagenome sequencing of whole community DNA. Fragment recruitments of metagenome sequence reads on the genome sequence of B. amyloliquefaciens FZB42 proved the presence of the strain in the rhizosphere over 5 weeks of the field trial. Comparison of taxonomic community profiles only revealed marginal changes after application of strain FZB42. The orders Burkholderiales, Actinomycetales and Rhizobiales were most abundant in all samples. Depending on plant age a general shift within the composition of the microbial communities that was independent of the application of strain FZB42 was observed. In addition to the taxonomic profiling, functional analysis of annotated sequences revealed no major differences between samples regarding application of the inoculant strain. PMID:24904564

Peanut (Arachis hypogaea L) is one of the widely cultivated and leading oilseed crops of the world and its yields are greatly affected by various biotic and abiotic stresses. Arachis diogoi, a wild relative of peanut, is an important source of genes for resistance against various stresses that affect peanut. In our previous study a thaumatin-like protein gene was found to be upregulated in a differential expression reverse transcription PCR (DDRT-PCR) study using the conidial spray of the late leaf spot pathogen, Phaeoisariopsis personata. In the present study, the corresponding full length cDNA was cloned using RACE-PCR and has been designated as AdTLP. It carried an open reading frame of 726 bp potentially capable of encoding a polypeptide of 241 amino acids with 16 conserved cysteine residues. The semi-quantitative RT-PCR analysis showed that the transcript level of AdTLP increased upon treatment with the late leaf spot pathogen of peanut, P. personata and various hormone treatments indicating its involvement in both, biotic and abiotic stresses. The antifungal activity of the purified recombinant protein was checked against different fungal pathogens, which showed enhanced anti-fungal activity compared to many other reported TLP proteins. The recombinant AdTLP-GFP fusion protein was found to be predominantly localized to extracellular spaces. Transgenic tobacco plants ectopically expressing AdTLP showed enhanced resistance to fungal pathogen, Rhizoctonia solani. The seedling assays showed enhanced tolerance of AdTLP transgenic plants against salt and oxidative stress. The transcript analysis of various defense related genes highlighted constitutively higher level expression of PR1a, PI-I and PI-II genes in transgenic plants. These results suggest that the AdTLP is a good candidate gene for enhancing stress resistance in crop plants. PMID:24367621

Antagonistic microorganisms against Rhizoctonia solani were isolated and their antifungal activities were investigated. Two hundred sixteen bacterial isolates were isolated from various soil samples and 19 isolates were found to antagonize the selected plant pathogenic fungi with varying degrees. Among them, isolate C9 was selected as an antagonistic microorganism with potential for use in further studies. Treatment with the selected isolate C9 resulted in significantly reduced incidence of stem-segment colonization by R. solani AG2-2(IV) in Zoysia grass and enhanced growth of grass. Through its biochemical, physiological, and 16S rDNA characteristics, the selected bacterium was identified as Bacillus subtilis subsp. subtilis. Mannitol (1%) and soytone (1%) were found to be the best carbon and nitrogen sources, respectively, for use in antibiotic production. An antibiotic compound, designated as DG4, was separated and purified from ethyl acetate extract of the culture broth of isolate C9. On the basis of spectral data, including proton nuclear magneric resonance (1H NMR), carbon nuclear magneric resonance (13C NMR), and mass analyses, its chemical structure was established as a stereoisomer of acetylbutanediol. Application of the ethyl acetate extract of isolate C9 to several plant pathogens resulted in dose-dependent inhibition. Treatment with the purified compound (an isomer of acetylbuanediol) resulted in significantly inhibited growth of tested pathogens. The cell free culture supernatant of isolate C9 showed a chitinase effect on chitin medium. Results from the present study demonstrated the significant potential of the purified compound from isolate C9 for use as a biocontrol agent as well as a plant growth promoter with the ability to trigger induced systemic resistance of plants. PMID:22783136

Sweetpotato storage roots are subjected to several forms of post harvest spoilage in the tropical climate during transportation from farmers' field to market and in storage. These are due to mechanical injury, weight loss, sprouting, and pests and diseases. Sweetpotato weevil is the single most important storage pest in tropical regions for which no control measures or resistant variety are yet available. Several microorganisms (mostly fungi) have been found to induce spoilage in stored sweetpotatoes. The most important among them are Botryodiplodia theobromae, Ceratocystis fimbriata, Fusarium spp., and Rhizopus oryzae. The other less frequently occurring spoilage microorganisms include Cochliobolus lunatus (Curvularia lunata), Macrophomina phaseolina, Sclerotium rolfsii, Rhizoctonia solani, Plenodomus destruens. Microbial spoilage of sweetpotato is found associated with decrease in starch, total sugar, organic acid (ascorbic acid and oxalic acid) contents with concomitant increase in polyphenols, ethylene, and in some instances phytoalexins. Several methods are used to control microbial spoilage. Curing to promote wound healing is found as the most suitable method to control microbial spoilage. Curing naturally occurs in tropical climates where mean day temperature during sweetpotato harvesting season (February-April) invariably remains at 32-35 degrees C and relative humidity at 80-95%. Sweetpotato varieties varied in their root dry matter content, and low root dry matter content attributed for their high curing efficiency. Curing efficiency of varieties also differed in response to curing periods. Fungicide treatment, bio-control, gamma irradiation, hydro warming, and storage in sand and saw dust were found to have intermediate impacts in controlling spoilage and enhancing shelf life of sweetpotato roots. Breeding program has to be chalked out to develop new varieties suitable to curing under tropical conditions in addition to developing varieties having multi-spectrum resistance to major post harvest rot pathogens and sweetpotato weevils. PMID:16371331

In the present study, out of 264 phosphate (P) solubilizing Bacillus strains isolated from apple rhizosphere, only twelve isolates were found to be efficient (showed most of the plant growth promoting activity) which were further characterized at molecular level using 16S rDNA partial gene sequencing. Out of 12 isolates, MZPSB 207 was found to be most efficient P-solubilizing (864.71 ?g/ml) isolate which also showed indole acetic acid production (51.83 ?g/ml), siderophore production, ammonia production, antagonistic property (against Rhizoctonia solani and Fusarium oxysporum), hydrolytic enzymes productions (protease, chitinase and cellulase), 1-aminocyclopropane-1-carboxylate (ACC) deaminase production (7.7 ?m ?KB mg(-1) h(-1)). The in-vitro seed germination assay showed that Bacillus (twelve isolates) inoculated seeds showed more seed germination and seedling vigor rate as compared to uninoculated control treatment. For the genetic diversity studies of efficient 12 strains, the polyphasic approach using 16S-rDNA, Repetitive element sequence (rep) based PCR (ERIC-PCR and BOX-PCR) were used. Based on 16S rDNA partial gene sequencing the isolated Bacillus genus was divide into four groups. First group (five isolates), second group (two isolates), third group (three isolates) and fourth group (two isolates) which showed close genetic relatedness to the B. subtilis, B. pumulis, B. megaterium and B. amyloliquefaciens, respectively. The rep PCR fingerprinting showed variability between and within the species. The large variability was showed by ERIC-PCR whereas some variability was showed by BOX-PCR. The results clearly showed that 16S rRNA gene sequencing is unable to discriminate the isolates at strain level. But rep-PCR fingerprinting is excellent tool to characterize and discriminate the strains at the genomic level. PMID:25279279

The present work was carried out to study the potential of plant rhizosphere associated bacteria for the biocontrol of potato black scurf disease caused by Rhizoctonia solani Khun AG-3. A total of twenty-eight bacteria isolated from diseased and healthy potato plants grown in the soil of Naran and Faisalabad, Pakistan were evaluated for their antagonistic potential. Nine bacterial strains were found to be antagonistic in vitro, reduced the fungal growth and caused the lysis of sclerotia of R. solani in dual culture assay as well as in extracellular metabolite efficacy test. The selected antagonistic strains were further tested for the production and efficacy of volatile and diffusible antibiotics, lytic enzymes and siderophores against R. solani. Selected antagonistic bacteria were also characterized for growth promoting attributes i.e., phosphate solubilization, nitrogen fixation and indole acetic acid production. Biocontrol efficacy and percent yield increase by these antagonists was estimated in greenhouse experiment. Statistical analysis showed that two Pseudomonas spp. StT2 and StS3 were the most effective with 65.1 and 73.9 percent biocontrol efficacy, as well as 87.3 and 98.3 percent yield increase, respectively. Potential antagonistic bacterial strain StS3 showed maximum homology to Pseudomonas sp. as determined by 16S rRNA gene sequencing. These results suggest that bacterial isolates StS3 and StT2 have excellent potential to be used as effective biocontrol agents promoting plant growth with reduced disease incidence. PMID:24031515

Using a gene disruption strategy, we generated mutants in the gliP locus of the plant-beneficial fungus Trichoderma virens that were no longer capable of producing gliotoxin. Phenotypic assays demonstrated that the gliP-disrupted mutants grew faster, were more sensitive to oxidative stress and exhibited a sparse colony edge compared with the WT strain. In a plate confrontation assay, the mutants deficient in gliotoxin production were ineffective as mycoparasites against the oomycete, Pythium ultimum, and the necrotrophic fungal pathogen, Sclerotinia sclerotiorum, but retained mycoparasitic ability against Rhizoctonia solani. Biocontrol assays in soil showed that the mutants were incapable of protecting cotton seedlings from attack by P. ultimum, against which the WT strain was highly effective. The mutants, however, were as effective as the WT strain in protecting cotton seedlings against R. solani. Loss of gliotoxin production also resulted in a reduced ability of the mutants to attack the sclerotia of S. sclerotiorum compared with the WT. The addition of exogenous gliotoxin to the sclerotia colonized by the mutants partially restored their degradative abilities. Interestingly, as in Aspergillus fumigatus, an opportunistic human pathogen, gliotoxin was found to be involved in pathogenicity of T. virens against larvae of the wax moth, Galleria mellonella. The loss of gliotoxin production in T. virens was restored by complementation with the gliP gene from A. fumigatus. We have, thus, demonstrated that the putative gliP cluster of T. virens is responsible for the biosynthesis of gliotoxin, and gliotoxin is involved in mycoparasitism and biocontrol properties of this plant-beneficial fungus. PMID:25082950

Arbuscular mycorrhizal fungi (AMF) are widespread soil microorganisms that associate mutualistically with plant hosts. AMF receive photosynthates from the host in return for various benefits. One of such benefits is in the form of enhanced pathogen tolerance. However, this aspect of the symbiosis has been understudied compared to effects on plant growth and its ability to acquire nutrients. While it is known that increased AMF species richness positively correlates with plant productivity, the relationship between AMF diversity and host responses to pathogen attack remains obscure. The objective of this study was to test whether AMF isolates can differentially attenuate the deleterious effects of a root pathogen on plant growth, whether the richest assemblage of AMF isolates provides the most tolerance against the pathogen, and whether AMF-induced changes to root architecture serve as a mechanism for improved plant disease tolerance. In a growth chamber study, we exposed the plant oxeye daisy (Leucanthemum vulgare) to all combinations of three AMF isolates and to the plant root pathogen Rhizoctonia solani. We found that the pathogen caused an 81% reduction in shoot and a 70% reduction in root biomass. AMF significantly reduced the highly deleterious effect of the pathogen. Mycorrhizal plants infected with the pathogen produced 91% more dry shoot biomass and 72% more dry root biomass relative to plants solely infected with R. solani. AMF isolate identity was a better predictor of AMF-mediated host tolerance to the pathogen than AMF richness. However, the enhanced tolerance response did not result from AMF-mediated changes to root architecture. Our data indicate that AMF communities can play a major role in alleviating host pathogen attack but this depends primarily on the capacity of individual AMF isolates to provide this benefit. PMID:23620744

Laser irradiation of soybean seeds for 3 min caused a clear reduction in the number of seed-borne fungi which became more pronounced as the irradiation time was extended. Pretreatment of the seeds with methylene blue, methyl red and carmine enhanced the effect of laser. Rhizoctonia solani, Alternaria tenuissima, Cercospora kikuchii and Colletotrichum truncatum were completely eliminated when the seeds were pretreated with a dye and irradiated for 10 min. Seed germination was stimulated on exposure of the seed to 1-min irradiation. At such dose, most of the dyes were accelerators while the higher doses were inhibitory to seed germination. Chlorophyll a, chlorophyll b and carotenoid content of developed plants differed, depending on the irradiation dose and dye treatment of the seeds. In seeds irradiated for 1 or 3 min, chlorophyll a formation was less affected than chlorophyll b formation. In seeds irradiated for 10 min, both the chlorophyll contents were decreased especially in the presence of some applied dyes. On the other hand, there was an increase in carotenoid content of soybean leaves when the laser dose increased. The number and dry mass of nodules were mostly greater (as compared to the corresponding control), when the seeds irradiated for 1 or 3 min were pretreated with methyl red, chlorophenol red, crystal violet and methylene blue. Irradiation of pre-sowing seeds greatly protected soybean stands against F. solani. The disease incidence differed somewhat when the irradiated seeds were pretreated with dyes. The reduction in disease incidence was accompanied by accumulation of high proline and phenol levels in the infected root tissues of soybean, suggesting that these compounds have a certain role in the prevention of disease development. PMID:10983234

Background Cynanchum komarovii Al Iljinski is a desert plant that has been used as analgesic, anthelminthic and antidiarrheal, but also as a herbal medicine to treat cholecystitis in people. We have found that the protein extractions from C. komarovii seeds have strong antifungal activity. There is strong interest to develop protein medication and antifungal pesticides from C. komarovii for pharmacological or other uses. Methodology/Principal Findings An antifungal protein with sequence homology to thaumatin-like proteins (TLPs) was isolated from C. komarovii seeds and named CkTLP. The three-dimensional structure prediction of CkTLP indicated the protein has an acid cleft and a hydrophobic patch. The protein showed antifungal activity against fungal growth of Verticillium dahliae, Fusarium oxysporum, Rhizoctonia solani, Botrytis cinerea and Valsa mali. The full-length cDNA was cloned by RT-PCR and RACE-PCR according to the partial protein sequences obtained by nanoESI-MS/MS. The real-time PCR showed the transcription level of CkTLP had a significant increase under the stress of abscisic acid (ABA), salicylic acid (SA), methyl jasmonate (MeJA), NaCl and drought, which indicates that CkTLP may play an important role in response to abiotic stresses. Histochemical staining showed GUS activity in almost the whole plant, especially in cotyledons, trichomes and vascular tissues of primary root and inflorescences. The CkTLP protein was located in the extracellular space/cell wall by CkTLP::GFP fusion protein in transgenic Arabidopsis. Furthermore, over-expression of CkTLP significantly enhanced the resistance of Arabidopsis against V. dahliae. Conclusions/Significance The results suggest that the CkTLP is a good candidate protein or gene for contributing to the development of disease-resistant crops. PMID:21364945

The Central Andean Highlands are the center of origin of the potato plant (Solanum tuberosum). Ages of mutualism between potato plants and soil bacteria in this region support the hypothesis that Andean soils harbor interesting plant growth-promoting (PGP) bacteria. Therefore, the aim of this study was to isolate rhizobacteria from Andean ecosystems, and to identify those with PGP properties. A total of 585 bacterial isolates were obtained from eight potato fields in the Andes and they were screened for suppression of Phytophthora infestans and Rhizoctonia solani. Antagonistic mechanisms were determined and antagonistic isolates were further tested for phosphate solubilization, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and production of NH3- and indole-3-acetic acid (IAA). PGP was studied in healthy and R. solani diseased plantlets under growth room conditions. Performance was compared to the commercial strain B. subtilis FZB24(®) WG. Isolates were dereplicated with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), and identified with 16S rRNA gene sequencing and multi locus sequence analysis (MLSA). A total of 10% of the isolates were effective antagonists, of which many were able to solubilize phosphate, and produce IAA, ACC deaminase, NH3 and hydrogen cyanide (HCN). During growth room experiments, 23 antagonistic isolates were associated with plant growth-promotion and/or disease suppression. Ten isolates had a statistically significant impact on test parameters compared to the uninoculated control. Three isolates significantly promoted plant growth in healthy plantlets compared to the commercial strain, and seven isolates outperformed the commercial strain in in vitro R. solani diseased plantlets. PMID:23333025

The fungal necrotrophic pathogen Rhizoctonia solani is a significant constraint to a range of crops as diverse as cereals, canola, and legumes. Despite wide-ranging germplasm screens in many of these crops, no strong genetic resistance has been identified, suggesting that alternative strategies to improve resistance are required. In this study, we characterize moderate resistance to R. solani anastomosis group 8 identified in Medicago truncatula. The activity of the ethylene- and jasmonate-responsive GCC box promoter element was associated with moderate resistance, as was the induction of the B-3 subgroup of ethylene response transcription factors (ERFs). Genes of the B-1 subgroup showed no significant response to R. solani infection. Overexpression of a B-3 ERF, MtERF1-1, in Medicago roots increased resistance to R. solani as well as an oomycete root pathogen, Phytophthora medicaginis, but not root knot nematode. These results indicate that targeting specific regulators of ethylene defense may enhance resistance to an important subset of root pathogens. We also demonstrate that overexpression of MtERF1-1 enhances disease resistance without apparent impact on nodulation in the A17 background, while overexpression in sickle reduced the hypernodulation phenotype. This suggests that under normal regulation of nodulation, enhanced resistance to root diseases can be uncoupled from symbiotic plant-microbe interactions in the same tissue and that ethylene/ERF regulation of nodule number is distinct from the defenses regulated by B-3 ERFs. Furthermore, unlike the stunted phenotype previously described for Arabidopsis (Arabidopsis thaliana) ubiquitously overexpressing B-3 ERFs, overexpression of MtERF1-1 in M. truncatula roots did not show adverse effects on plant development. PMID:20713618

Bacteria were isolated from roots of sugarcane varieties grown in the fields of Punjab. They were identified by using API20E/NE bacterial identification kits and from sequences of 16S rRNA and amplicons of the cpn60 gene. The majority of bacteria were found to belong to the genera of Enterobacter, Pseudomonas, and Klebsiella, but members of genera Azospirillum, Rhizobium, Rahnella, Delftia, Caulobacter, Pannonibacter, Xanthomonas, and Stenotrophomonas were also found. The community, however, was dominated by members of the Pseudomonadaceae and Enterobacteriaceae, as representatives of these genera were found in samples from every variety and location examined. All isolates were tested for the presence of five enzymes and seven factors known to be associated with plant growth promotion. Ten isolates showed lipase activity and eight were positive for protease activity. Cellulase, chitinase, and pectinase were not detected in any strain. Nine strains showed nitrogen fixing ability (acetylene reduction assay) and 26 were capable of solubilizing phosphate. In the presence of 100 mg/l tryptophan, all strains except one produced indole acetic acid in the growth medium. All isolates were positive for ACC deaminase activity. Six strains produced homoserine lactones and three produced HCN and hexamate type siderophores. One isolate was capable of inhibiting the growth of 24 pathogenic fungal strains of Colletotrichum, Fusarium, Pythium, and Rhizoctonia spp. In tests of their abilities to grow under a range of temperature, pH, and NaCl concentrations, all isolates grew well on plates with 3% NaCl and most of them grew well at 4 to 41degrees C and at pH 11. PMID:21193815

Chitinases have the ability of chitin digestion that constitutes a main compound of the cell wall in many of the phytopathogens such as fungi. In the following investigation, a novel chitinase with antifungal activity was characterized from a native Serratia marcescens B4A. Partially purified enzyme had an apparent molecular mass of 54 kDa. It indicated an optimum activity in pH 5 at 45°C. Enzyme was stable in 55°C for 20 min and at a pH range of 3–9 for 90 min at 25°C. When the temperature was raised to 60°C, it might affect the structure of enzymes lead to reduction of chitinase activity. Moreover, the Km and Vmax values for chitin were 8.3 mg/ml and 2.4 mmol/min, respectively. Additionally, the effect of some cations and chemical compounds were found to stimulate the chitinase activity. In addition, Iodoacetamide and Idoacetic acid did not inhibit enzyme activity, indicating that cysteine residues are not part of the catalytic site of chitinase. Finally, chitinase activity was further monitored by scanning electronic microscopy data in which progressive changes in chitin porosity appeared upon treatment with chitinase. This enzyme exhibited antifungal activity against Rhizoctonia solani, Bipolaris sp, Alternaria raphani, Alternaria brassicicola, revealing a potential application for the industry with potentially exploitable significance. Fungal chitin shows some special features, in particular with respect to chemical structure. Difference in chitinolytic ability must result from the subsite structure in the enzyme binding cleft. This implies that why the enzyme didn’t have significant antifungal activity against other Fungi. PMID:24031719

Background Trichoderma is a genus of mycotrophic filamentous fungi (teleomorph Hypocrea) which possess a bright variety of biotrophic and saprotrophic lifestyles. The ability to parasitize and/or kill other fungi (mycoparasitism) is used in plant protection against soil-borne fungal diseases (biological control, or biocontrol). To investigate mechanisms of mycoparasitism, we compared the transcriptional responses of cosmopolitan opportunistic species and powerful biocontrol agents Trichoderma atroviride and T. virens with tropical ecologically restricted species T. reesei during confrontations with a plant pathogenic fungus Rhizoctonia solani. Results The three Trichoderma spp. exhibited a strikingly different transcriptomic response already before physical contact with alien hyphae. T. atroviride expressed an array of genes involved in production of secondary metabolites, GH16 ß-glucanases, various proteases and small secreted cysteine rich proteins. T. virens, on the other hand, expressed mainly the genes for biosynthesis of gliotoxin, respective precursors and also glutathione, which is necessary for gliotoxin biosynthesis. In contrast, T. reesei increased the expression of genes encoding cellulases and hemicellulases, and of the genes involved in solute transport. The majority of differentially regulated genes were orthologues present in all three species or both in T. atroviride and T. virens, indicating that the regulation of expression of these genes is different in the three Trichoderma spp. The genes expressed in all three fungi exhibited a nonrandom genomic distribution, indicating a possibility for their regulation via chromatin modification. Conclusion This genome-wide expression study demonstrates that the initial Trichoderma mycotrophy has differentiated into several alternative ecological strategies ranging from parasitism to predation and saprotrophy. It provides first insights into the mechanisms of interactions between Trichoderma and other fungi that may be exploited for further development of biofungicides. PMID:23432824

Species that inhabit phosphorus- (P) and micronutrient-impoverished soils typically have adaptations to enhance the acquisition of these nutrients, for example cluster roots in Proteaceae. However, there are several species co-occurring in the same environment that do not produce similar specialised roots. This study aims to investigate whether one of these species (Scholtzia involucrata) can benefit from the mobilisation of P or micronutrients by the cluster roots of co-occurring Banksia attenuata, and also to examine the response of B. attenuata to the presence of S. involucrata. We conducted a greenhouse experiment, using a replacement series design, where B. attenuata and S. involucrata shared a pot at proportions of 2:0, 1:2 and 0:4. S. involucrata plants grew more in length, were heavier and had higher manganese (Mn) concentrations in their young leaves when grown next to one individual of B. attenuata and one individual of S. involucrata than when grown with three conspecifics. All S. involucrata individuals were colonised by arbuscular mycorrhizal fungi, and possibly Rhizoctonia. Additionally, P concentration was higher in the young leaves of B. attenuata when grown with another B. attenuata than when grown with two individuals of S. involucrata, despite the smaller size of the S. involucrata individuals. Our results demonstrate that intraspecific competition was stronger than interspecific competition for S. involucrata, but not for B. attenuata. We conclude that cluster roots of B. attenuata facilitate the acquisition of nutrients by neighbouring shrubs by making P and Mn more available for their neighbours. PMID:23934064

Knowledge of the incubation period of infectious diseases (time between host infection and expression of disease symptoms) is crucial to our epidemiological understanding and the design of appropriate prevention and control policies. Plant diseases cause substantial damage to agricultural and arboricultural systems, but there is still very little information about how the incubation period varies within host populations. In this paper, we focus on the incubation period of soilborne plant pathogens, which are difficult to detect as they spread and infect the hosts underground and above-ground symptoms occur considerably later. We conducted experiments on Rhizoctonia solani in sugar beet, as an example patho-system, and used modelling approaches to estimate the incubation period distribution and demonstrate the impact of differing estimations on our epidemiological understanding of plant diseases. We present measurements of the incubation period obtained in field conditions, fit alternative probability models to the data, and show that the incubation period distribution changes with host age. By simulating spatially-explicit epidemiological models with different incubation-period distributions, we study the conditions for a significant time lag between epidemics of cryptic infection and the associated epidemics of symptomatic disease. We examine the sensitivity of this lag to differing distributional assumptions about the incubation period (i.e. exponential versus Gamma). We demonstrate that accurate information about the incubation period distribution of a pathosystem can be critical in assessing the true scale of pathogen invasion behind early disease symptoms in the field; likewise, it can be central to model-based prediction of epidemic risk and evaluation of disease management strategies. Our results highlight that reliance on observation of disease symptoms can cause significant delay in detection of soil-borne pathogen epidemics and mislead practitioners and epidemiologists about the timing, extent, and viability of disease control measures for limiting economic loss. PMID:24466153

From the fruiting bodies of the mushroom Lyophyllum shimeji, a novel ribosome inactivating protein with a molecular weight of 20 kDa and exhibiting antifungal activity against Physalospora piricola (IC(50) = 2.5 microM) and Coprinus comatus was isolated. The protein, designated lyophyllin, was purified by ion exchange chromatography on CM-cellulose, affinity chromatography on Affi-gel Blue Gel, and then ion exchange chromatography on Mono S. Lyophyllin possessed an N-terminal sequence with some similarity to those of plant ribosome-inactivating proteins. It inhibited translation in rabbit reticulocyte lysate with an IC(50) of 1 nM, thymidine uptake by murine splenocytes with an IC(50) of 1 microM and HIV-1 reverse transcriptase activity with an IC(50) of 7.9 nM. Lyophyllin did not manifest ribonuclease or hemagglutinating activity. An antifungal protein, designated Lyophyllum antifungal protein (LAP), with a molecular weight of 14 kDa, and an N-terminal sequence somewhat analogous to those of angiosperm thaumatin-like proteins and thaumatins and an inactive variant of the ubiquitin-conjugating enzyme, was first isolated from Lyophyllum shimeji. LAP was adsorbed on CM-cellulose, Affi-gel blue gel, and Mono S. LAP exerted antifungal activity against P. piricola (IC(50) = 70 nM) and Mycosphaerella arachidicola but not against Rhizoctonia solani, Colletotrichum gossypii, and Coprinus comatus. It exerted very low translation inhibitory activity in a rabbit reticulocyte lysate system (IC(50) = 70 microM) and negligible ribonuclease activity toward yeast transfer RNA and hemagglutinating activity toward rabbit erythrocytes. It inhibited HIV-1 reverse transcriptase with an IC(50) of about 5.2 nM. A synergism in antifungal activities of LAP and lyophyllin against P. piricola was demonstrable. PMID:11556814

To study the effect of microenvironments on potato-associated bacteria, the abundance and diversity of bacteria isolated from the rhizosphere, phyllosphere, endorhiza, and endosphere of field grown potato was analyzed. Culturable bacteria were obtained after plating on R2A medium. The endophytic populations averaged 10(3) and 10(5) CFU/g (fresh wt.) for the endosphere and endorhiza. respectively, which were lower than those for the ectophytic microenvironments, with 10(5) and 10(7) CFU/g (fresh wt.) for the phyllosphere and rhizosphere, respectively. The composition and richness of bacterial species was microenvironment-dependent. The occurrence and diversity of potato-associated bacteria was additionally monitored by a cultivation-independent approach using terminal restriction fragment length polymorphism analysis of 16S rDNA. The patterns obtained revealed a high heterogeneity of community composition and suggested the existence of microenvironment-specific communities. In an approach to measure the antagonistic potential of potato-associated bacteria, a total of 440 bacteria was screened by dual testing for in vitro antagonism towards the soilborne pathogens Verticillium dahliae and Rhizoctonia solani. The proportion of isolates with antagonistic activity was highest for the rhizosphere (10%), followed by the endorhiza (9%), phyllosphere (6%), and endosphere (5%). All 33 fungal antagonists were characterized by testing their in vitro antagonistic mechanisms, including their glucanolytic, chitinolytic, pectinolytic, cellulolytic, and proteolytic activity, and by their BOX-PCR fingerprints. In addition, they were screened for their biocontrol activity against Meloidogyne incognita. Overall, nine isolates belonging to Pseudomonas and Streptomyces species were found to control both fungal pathogens and M. incognita and were therefore considered as promising biological control agents. PMID:12455609

Application of the plant associated bacterium Bacillus amyloliquefaciens FZB42 on lettuce (Lactuca sativa) confirmed its capability to promote plant growth and health by reducing disease severity (DS) caused by the phytopathogenic fungus Rhizoctonia solani. Therefore this strain is commercially applied as an eco-friendly plant protective agent. It is able to produce cyclic lipopeptides (CLP) and polyketides featuring antifungal and antibacterial properties. Production of these secondary metabolites led to the question of a possible impact of strain FZB42 on the composition of microbial rhizosphere communities after its application. Rating of DS and lettuce growth during a field trial confirmed the positive impact of strain FZB42 on the health of the host plant. To verify B. amyloliquefaciens as an environmentally compatible plant protective agent, its effect on the indigenous rhizosphere community was analyzed by metagenome sequencing. Rhizosphere microbial communities of lettuce treated with B. amyloliquefaciens FZB42 and non-treated plants were profiled by high-throughput metagenome sequencing of whole community DNA. Fragment recruitments of metagenome sequence reads on the genome sequence of B. amyloliquefaciens FZB42 proved the presence of the strain in the rhizosphere over 5 weeks of the field trial. Comparison of taxonomic community profiles only revealed marginal changes after application of strain FZB42. The orders Burkholderiales, Actinomycetales and Rhizobiales were most abundant in all samples. Depending on plant age a general shift within the composition of the microbial communities that was independent of the application of strain FZB42 was observed. In addition to the taxonomic profiling, functional analysis of annotated sequences revealed no major differences between samples regarding application of the inoculant strain. PMID:24904564

Background Turfgrass species are agriculturally and economically important perennial crops. Turfgrass species are highly susceptible to a wide range of fungal pathogens. Dollar spot and brown patch, two important diseases caused by fungal pathogens Sclerotinia homoecarpa and Rhizoctonia solani, respectively, are among the most severe turfgrass diseases. Currently, turf fungal disease control mainly relies on fungicide treatments, which raises many concerns for human health and the environment. Antimicrobial peptides found in various organisms play an important role in innate immune response. Methodology/Principal Findings The antimicrobial peptide - Penaeidin4-1 (Pen4-1) from the shrimp, Litopenaeus setiferus has been reported to possess in vitro antifungal and antibacterial activities against various economically important fungal and bacterial pathogens. In this study, we have studied the feasibility of using this novel peptide for engineering enhanced disease resistance into creeping bentgrass plants (Agrostis stolonifera L., cv. Penn A-4). Two DNA constructs were prepared containing either the coding sequence of a single peptide, Pen4-1 or the DNA sequence coding for the transit signal peptide of the secreted tobacco AP24 protein translationally fused to the Pen4-1 coding sequence. A maize ubiquitin promoter was used in both constructs to drive gene expression. Transgenic turfgrass plants containing different DNA constructs were generated by Agrobacterium-mediated transformation and analyzed for transgene insertion and expression. In replicated in vitro and in vivo experiments under controlled environments, transgenic plants exhibited significantly enhanced resistance to dollar spot and brown patch, the two major fungal diseases in turfgrass. The targeting of Pen4-1 to endoplasmic reticulum by the transit peptide of AP24 protein did not significantly impact disease resistance in transgenic plants. Conclusion/Significance Our results demonstrate the effectiveness of Pen4-1 in a perennial species against fungal pathogens and suggest a potential strategy for engineering broad-spectrum fungal disease resistance in crop species. PMID:21931807

Invasive soilborne plant pathogens cause substantial damage to crops and natural populations, but our understanding of how to prevent their epidemics or reduce their damage is limited. A key and experimentally-tested concept in the epidemiology of soilborne plant diseases is that of a threshold spacing between hosts below which epidemics (invasive spread) can occur. We extend this paradigm by examining how plant-root growth may alter the conditions for occurrence of soilborne pathogen epidemics in plant populations. We hypothesise that host-root growth can 1) increase the probability of pathogen transmission between neighbouring plants and, consequently, 2) decrease the threshold spacing for epidemics to occur. We predict that, in systems initially below their threshold conditions, root growth can trigger soilborne pathogen epidemics through a switch from non-invasive to invasive behaviour, while in systems above threshold conditions root growth can enhance epidemic development. As an example pathosystem, we studied the fungus Rhizoctonia solani on sugar beet in field experiments. To address hypothesis 1, we recorded infections within inoculum-donor and host-recipient pairs of plants with differing spacing. We translated these observations into the individual-level concept of pathozone, a host-centred form of dispersal kernel. To test hypothesis 2 and our prediction, we used the pathozone to parameterise a stochastic model of pathogen spread in a host population, contrasting scenarios of spread with and without host growth. Our results support our hypotheses and prediction. We suggest that practitioners of agriculture and arboriculture account for root system expansion in order to reduce the risk of soilborne-disease epidemics. We discuss changes in crop design, including increasing plant spacing and using crop mixtures, for boosting crop resilience to invasion and damage by soilborne pathogens. We speculate that the disease-induced root growth observed in some pathosystems could be a pathogen strategy to increase its population through host manipulation. PMID:23667560

Polygalacturonase inhibiting proteins (PGIPs) are the major defense proteins which play an important role in resistance to infection of pathogens. A putative novel gene encoding PGIP was isolated from Panax ginseng C.A. Meyer, which shows 70.3 and 68.4% homology with chick pea and Arabidopsis PGIPs. The RACE PCR was preformed to isolate the full-length PGIP cDNA from Panax ginseng. Sequence analysis revealed that the cDNA of PgPGIP is of 1,275 bp in length and that it's containing ORF encodes for a polypeptide of 366 amino acids. Domain analysis revealed that the deduced amino acid sequences of PgPGIP have a typical PGIP topology. The transcription level of PgPGIP was up-regulated in ginseng in response to wounding and infection with phytopathogenic fungi i.e., Rhizoctonia solani, Fusarium oxysporum, Phythium ultimum, Botrytis cinerea, Colletotrichum gloeosporioides and Cylindrocarpon destructans, which causes drastic damage in ginseng plants. The constitutive PgPGIP expression of 4 years old plant, showed elevated transcript level, especially roots, showed maximum then buds, stems and leaves, indicating that the gene is developmentally regulated. The crude PGIP extracts derived from the fungal infected plants directly reduces the aggressive potential of PGs from diverse group of fungi. Like other PGIPs, PgPGIP also possess board spectrum of inhibitory activity. Thus, the presence of PgPGIP gene and their active role in defense mechanism was proved. The structural model of PgPGIP was predicted based on the alignment generated by EBI-Align, the program "MOODELLER" and the predicted structure showed 10 ?-strands and 10 ?-helixes region. PMID:19946753

Rhizosphere competence of bacterial inoculants is assumed to be important for successful biocontrol. Knowledge of factors influencing rhizosphere competence under field conditions is largely lacking. The present study is aimed to unravel the effects of soil types on the rhizosphere competence and biocontrol activity of the two inoculant strains Pseudomonas jessenii RU47 and Serratia plymuthica 3Re4-18 in field-grown lettuce in soils inoculated with Rhizoctonia solani AG1-IB or not. Two independent experiments were carried out in 2011 on an experimental plot system with three soil types sharing the same cropping history and weather conditions for more than 10 years. Rifampicin resistant mutants of the inoculants were used to evaluate their colonization in the rhizosphere of lettuce. The rhizosphere bacterial community structure was analyzed by denaturing gradient gel electrophoresis of 16S rRNA gene fragments amplified from total community DNA to get insights into the effects of the inoculants and R. solani on the indigenous rhizosphere bacterial communities. Both inoculants showed a good colonization ability of the rhizosphere of lettuce with more than 106 colony forming units per g root dry mass two weeks after planting. An effect of the soil type on rhizosphere competence was observed for 3Re4-18 but not for RU47. In both experiments a comparable rhizosphere competence was observed and in the presence of the inoculants disease symptoms were either significantly reduced, or at least a non-significant trend was shown. Disease severity was highest in diluvial sand followed by alluvial loam and loess loam suggesting that the soil types differed in their conduciveness for bottom rot disease. Compared to effect of the soil type of the rhizosphere bacterial communities, the effects of the pathogen and the inoculants were less pronounced. The soil types had a surprisingly low influence on rhizosphere competence and biocontrol activity while they significantly affected the bottom rot disease severity. PMID:25099168

Seventy-five percent of the peanuts (Arachus hypogaia) produced in the United States are grown in the Atlantic Coastal Plain region. Portions of this area, including Alabama and Georgia, exhibit a subtropical climate that promotes soil-borne plant fungal diseases. Most fields receive repeated fungicide applications during the growing season to suppress the disease causing organisms, such as Sclerotium rolfsii, Rhizoctonia solani, and Cylindrocladium parasiticum. Information regarding fungicide effects on the soil microbial community, with components principally responsible for transformation and fate of fungicides and other soil-applied pesticides, is limited. The objectives of the study were to assess soil microbial community response to (1) varying rates of the sterol-inhibiting fungicide tebuconazole (0, single application, season max, 2x season max), and (2) field rates of the sterol-inhibitors cyproconazole, prothioconazole, tebuconazole, and flutriafol, and thiol-competitor chlorothalonil. The sterol-inhibitors exhibited different half lives, as listed in the FOOTPRINT database, ranging from <1 day to >1300 d. Chlorothalonil was chosen because it is the most frequently applied fungicide to peanut. Shifts in the fungi, gram positive and gram negative bacteria, were monitored during the experiments using phospholipid fatty acid (PLFA) profiles. Ergosterol levels and pesticide decay rates were also monitored to evaluate the effectiveness of the fungicide and soil residence time, respectively. In the rate study, the highest rate of tebuconazole reduced the fungal biomarker 18:2?6,9c to 2.6 nmol g-1 dry soil at 17 d, as compared to the control (4.1 nmol g-1 dry soil). However, levels of the fungal PLFA biomarker were similar regardless of rate at 0 and 32 d. The gram negative bacterial PLFA mole percent was greater at 17 d for the two highest rates of tebuconazole, but was similar at 0 and 32 d. Gram positive and fungal mole percents were not affected at any time point. Tebuconazole half life was approximately 10 d regardless of rate. A principle components analysis revealed negligible fungicide impact on PLFA. In the field rate study soil samples were collected immediately following fungicide application to peanut. A laboratory dissipation study, accompanied by PLFA and ergosterol analysis is currently being conducted. Results from the rate experiment indicate that tebuconazole's effect was transient due to rapid dissipation and suggest a gram negative bacterial role. Results obtained from both studies will be useful in predicting the environmental fate and impact of fungicides commonly used for production of peanut and other crops on soil microorganisms.

Background Induced resistance is a state of enhanced defensive capacity developed by a plant reacting to specific biotic or chemical stimuli. Over the years, several forms of induced resistance have been characterized, including systemic acquired resistance, which is induced upon localized infection by an avirulent necrotizing pathogen, and induced systemic resistance (ISR), which is elicited by selected strains of nonpathogenic rhizobacteria. However, contrary to the relative wealth of information on inducible defense responses in dicotyledoneous plants, our understanding of the molecular mechanisms underlying induced resistance phenomena in cereal crops is still in its infancy. Using a combined cytomolecular and pharmacological approach, we analyzed the host defense mechanisms associated with the establishment of ISR in rice by the rhizobacterium Serratia plymuthica IC1270. Results In a standardized soil-based assay, root treatment with IC1270 rendered foliar tissues more resistant to the hemibiotrophic pathogen Magnaporthe oryzae, causal agent of the devastating rice blast disease. Analysis of the cytological and biochemical alterations associated with restriction of fungal growth in IC1270-induced plants revealed that IC1270 primes rice for enhanced attacker-induced accumulation of reactive oxygen species (ROS) and autofluorescent phenolic compounds in and near epidermal cells displaying dense cytoplasmic granulation. Similar, yet more abundant, phenotypes of hypersensitively dying cells in the vicinity of fungal hyphae were evident in a gene-for-gene interaction with an avirulent M. oryzae strain, suggesting that IC1270-inducible ISR and R protein conditioned effector-triggered immunity (ETI) target similar defense mechanisms. Yet, this IC1270-inducible ISR response seems to act as a double-edged sword within the rice defense network as induced plants displayed an increased vulnerability to the necrotrophic pathogens Rhizoctonia solani and Cochliobolus miyabeanus. Artificial enhancement of ROS levels in inoculated leaves faithfully mimicked the opposite effects of IC1270 bacteria on aforementioned pathogens, suggesting a central role for oxidative events in the IC1270-induced resistance mechanism. Conclusion Besides identifying ROS as modulators of antagonistic defense mechanisms in rice, this work reveals the mechanistic similarities between S. plymuthica-mediated ISR and R protein-dictated ETI and underscores the importance of using appropriate innate defense mechanisms when breeding for broad-spectrum rice disease resistance. PMID:19161601

Plant cells produce a vast amount of secondary metabolites. Production of some compounds is restricted to a single species. Some compounds are nearly always found only in certain specific plant organs and during a specific developmental period of the plant. Some secondary metabolites of plants serve as defensive compounds against invading microorganisms. Nowadays, it is attempted to substitute the biological and natural agents with chemically synthesized fungicides. In the present research, the antifungal activities of essential oils of seven medicinal plants on mycelial growth of three soilborne plant pathogenic fungi were investigated. The plants consisted of Zataria multiflora, Thymus carmanicus, Mentha pieperata, Satureja hortensis, Lavandual officinolis, Cuminum cyminum and Azadirachta indica. The first five plants are from the family Labiatae. Examined fungi, Fusarium oxysporum f.sp. lycopersici, Fusarium solani and Rhizoctonia solani are the causal agents of tomato root rot. Essential oils of Z. multiflora, T. carmanicus, M. pieperata, S. hortensis and C. cyminum were extracted by hydro-distillation method. Essential oils of L. officinalis and A. indica were extracted by vapor-distillation method. A completely randomized design with five replicates was used to examine the inhibitory impact of each concentration (300, 600 and 900 ppm) of each essential oil. Poisoned food assay using potato dextrose agar (PDA) medium was employed. Results showed that essential oils of A. indica, Z. multiflora, T. carmanicus and S. hortensis in 900 ppm at 12 days post-inoculation, when the control fungi completely covered the plates, prevented about 90% from mycelial growth of each of the fungi. While, the essential oils of M. pieperata, C. cyminum and L. officinalis in the same concentration and time prevented 54.86, 52.77 and 48.84%, respectively, from F. solani growth. These substances did not prevent from F. oxysporum f.sp. lycopersici and R. solani growth. Minimum inhibitory concentration (MIC) of essential oils of T. carmanicus, Z. multiflora and A. indica from R. solani and F. solani growth was 900 and 600 ppm, respectively. In addition, the MIC of essential oils of these plants and essential oil of S. hortensis from F. oxysporum f.sp. lycopersici growth was 900 ppm. The MIC of essential oils of M. pieperata, C. cyminum and L. officinalis from F. solani growth was 900 ppm. PMID:22702190

Rhizoctonia solani, Fusarium solani, F. oxysporum, and Macrophomina phaseolina were found to be associated with root rott and wilt symptoms of faba bean plants collected from different fieldes in New Valley governorate, Egypt. All the obtained isolates were able to attack faba bean plants (cv. Giza 40) causing damping-off and root rot/wilt diseases. R. solani isolates 2 and 5, F. solani isolate 8, F. oxysporum isolate 12 and M. phaseolina isolate 14 were the more virulent ones in the pathogenicity tests. Biocontrol agents (Trichoderma viride and Bacillus megaterium) and chemical inducers (salicylic acid [SA] and hydrogen peroxide) individually or in combination were examined for biological control of damping-off and root rot/wilt and growth promoting of faba bean plants in vitro and in vivo. Both antagonistic biocontrol agents and chemical inducers either individually or in combination inhibited growth of the tested pathogenic fungi. Biocontrol agents combined with chemical inducers recorded the highest inhibited growth especially in case SA + T. viride and SA + B. megaterium. Under green house and field conditions, all treatments significantly reduced damping-off and root rot/wilt severity and increased of survival plants. Also, these treatments increased fresh and weights of the survival plants in pots compared with control. The combination between biocontrol agents and chemical inducers were more effective than used of them individually and SA + T. viride was the best treatment in this respect. Also, under field conditions, all these treatments significantly increased growth parameters (plant height and number of branches per plant) and yield components (number of pods per plant and number of seeds per plant, weight of 100 seeds and total yield per feddan) and protein content in both seasons (2010~2011 and 2011~2012). Faba bean seeds soaked in SA + T. viride and SA + B. megaterium were recorded the highest growth parameters and yield components. Generally, the combination between biocontrol agents and chemical inducers recorded the best results for controlling damping-off and root rot/wilt diseases in greenhouse and field with addition improved plant growth and increased yield components in field. PMID:23610539

During 2005, Belgium enforced a strict procedure for the assignment of critical-use permits for methyl bromide (MeBr) as a soil disinfestant. This procedure involved an inspection of the site before disinfestation by a representative of a registered institute, and a mandatory demonstration of the presence of a pest or disease for which a critical use permit could be granted according to the Critical Use Nominations (CUNs). The procedure was subject to random inspections by an independent institute. The results of these inspections demonstrated proper and timely evaluation of the permit requests. A total of 113 requests for a MeBr disinfestation permit were submitted in 2005. Out of these, 105 referred to applications in 2005. The remaining 8 requests referred to applications in 2006 and were denied a permit based on the lack of MeBr quotum granted to Belgium for 2006. Of the 105 requests for applications in 2005, 93 received a MeBr application permit for soil disinfestation. These 93 permits represented 15911 kg or 37.3% of the total quotum assigned to Belgium in 2005 (42676 kg). Most of the quotum was used for butterhead lettuce (11456 kg or 72% of the applied MeBr). For most commodities, a surplus in quotum was available. However, for chrysanthemum, the amount requested for critical use exceeded the available quotum. The most important pests and diseases for which a permit was assigned were Meloidogyne, Sclerotinia, Rhizoctonia, Olpidium, Pythium, Pyrenochaeta, Verticillium, and a combination of these fungi and nematodes. The 12 requests for which no permit was granted represented 2010 kg or 11.3% of the total amount requested. In addition, institutes carrying out the assignment procedure reported at least 62 extra cases where they had been contacted by a grower but where no official permit request was filed based on the first inspection. When including those cases, the total reduction of the potentially used amount of MeBr is about 44 %. When adding an estimated 10 to 15% reduction due to the use of alternatives by growers who did not start the permit assignment procedure, the total reduction is approximately 50-55%. PMID:17390790

The actinomycete Streptomyces lydicus WYEC108 showed strong in vitro antagonism against various fungal plant pathogens in plate assays by producing extracellular antifungal metabolites. When Pythium ultimum or Rhizoctonia solani was grown in liquid medium with S. lydicus WYEC108, inhibition of growth of the fungi was observed. When WYEC108 spores or mycelia were used to coat pea seeds, the seeds were protected from invasion by P. ultimum in an oospore-enriched soil. While 100% of uncoated control seeds were infected by P. ultimum within 48 h after planting, less than 40% of coated seeds were infected. When the coated seeds were planted in soil 24 h prior to introduction of the pathogen, 96 h later, less than 30% of the germinating seeds were infected. Plant growth chamber studies were also carried out to test for plant growth effects and for suppression by S. lydicus WYEC108 of Pythium seed rot and root rot. When WYEC108 was applied as a spore-peat moss-sand formulation (10(8) CFU/g) to P. ultimum-infested sterile or nonsterile soil planted with pea and cotton seeds, significant increases in average plant stand, plant length, and plant weight were observed in both cases compared with untreated control plants grown in similar soils. WYEC108 hyphae colonized and were able to migrate downward with the root as it elongated. Over a period of 30 days, the population of WYEC108 colonized emerging roots of germinating seeds and remained stable (10(5) CFU/g) in the rhizosphere, whereas the nonrhizosphere population of WYEC108 declined at least 100-fold (from 10(5) to 10(3) or fewer CFU/g). The stability of the WYEC108 population incubated at 25 degrees C in the formulation, in sterile soil, and in nonsterile soil was also evaluated. In all three environments, the population of WYEC108 maintained its size for 90 days or more. When pea, cotton, and sweet corn seeds were placed into sterile and nonsterile soils containing 10(6) or more CFU of WYEC108 per g, it colonized the emerging roots. After a 1-week growing period, WYEC108 populations of 10(5) CFU/g (wet weight) of root were found on pea roots in the amended sterile soil environment versus 10(4) CFU/g in amended nonsterile soil. To further study the in vitro interaction between the streptomycete and P. ultimum, mycelia of WYEC108 were mixed with oospores of P. ultimum in agar, which was then used as a film to coat slide coverslips.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7487043

The actinomycete Streptomyces lydicus WYEC108 showed strong in vitro antagonism against various fungal plant pathogens in plate assays by producing extracellular antifungal metabolites. When Pythium ultimum or Rhizoctonia solani was grown in liquid medium with S. lydicus WYEC108, inhibition of growth of the fungi was observed. When WYEC108 spores or mycelia were used to coat pea seeds, the seeds were protected from invasion by P. ultimum in an oospore-enriched soil. While 100% of uncoated control seeds were infected by P. ultimum within 48 h after planting, less than 40% of coated seeds were infected. When the coated seeds were planted in soil 24 h prior to introduction of the pathogen, 96 h later, less than 30% of the germinating seeds were infected. Plant growth chamber studies were also carried out to test for plant growth effects and for suppression by S. lydicus WYEC108 of Pythium seed rot and root rot. When WYEC108 was applied as a spore-peat moss-sand formulation (10(8) CFU/g) to P. ultimum-infested sterile or nonsterile soil planted with pea and cotton seeds, significant increases in average plant stand, plant length, and plant weight were observed in both cases compared with untreated control plants grown in similar soils. WYEC108 hyphae colonized and were able to migrate downward with the root as it elongated. Over a period of 30 days, the population of WYEC108 colonized emerging roots of germinating seeds and remained stable (10(5) CFU/g) in the rhizosphere, whereas the nonrhizosphere population of WYEC108 declined at least 100-fold (from 10(5) to 10(3) or fewer CFU/g). The stability of the WYEC108 population incubated at 25 degrees C in the formulation, in sterile soil, and in nonsterile soil was also evaluated. In all three environments, the population of WYEC108 maintained its size for 90 days or more. When pea, cotton, and sweet corn seeds were placed into sterile and nonsterile soils containing 10(6) or more CFU of WYEC108 per g, it colonized the emerging roots. After a 1-week growing period, WYEC108 populations of 10(5) CFU/g (wet weight) of root were found on pea roots in the amended sterile soil environment versus 10(4) CFU/g in amended nonsterile soil. To further study the in vitro interaction between the streptomycete and P. ultimum, mycelia of WYEC108 were mixed with oospores of P. ultimum in agar, which was then used as a film to coat slide coverslips.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7487043

Iran is considered a major genetic for medicinal plant in the world. Because of this significant diversity and historical background in identification and utilization to remedy human and animal diseases, export of medicinal plant can help to strengthen local as well as natural economy. Buglosse (Fig. 1) is one of the most important and common medicinal plants in Iran and exist as Echium amoneum and Borago officinalis. This work was conducted in order to identify the causal agent(s) of damping off disease in buglosse. Plant disease samples were taken from Esfahan and Tehran provinces. Symptoms on original plant including root, crown rot, dark tissue, pith and hallow root were collected in order to isolate disease agent(s). Symptomatic root and crown tissues after surface sterilization with 96% ethanol were transferred on to PDA and WA media and also on moist filter paper in petri dishes. Two fungal colonies grew from tissue segments and spore culture was subsequently purified. The fungal isolate identified as Rhizoctonia solani based on the following test. Hyphal tip was removed from colony margin placed on PDA and PSA media and incubated in dark. Colony diameter of one hundred hyphae measured and nucleus was stained according to Bandoni (1979), Kronland and Stanghellini (1988). It was observed that in each cell of hyphae there are more than two nuclei. Single spore culture were obtained from macroconidia of Fusarium isolate. After 24 hr of incubation, growing single spore were transferred to KCL medium to detect spore chains. Fungal isolates transferred to PSA and PDA media for sporulation. After 7 days colonies appeared as white cream to pinkish on top and cream to dark pink at the bottom of petri dish with abundant micro and macro conidia. Colonies were snow white, felting shape, with ample causal hyphae on PSA medium. On KCL medium, fungal growth was superficial and colonies were colorless with long macroconidia and individual sausage-shape macroconidia being thinner one side and having maximum four septa. Microconidia were long double compartment round on both side, straight to slightly curved. Base on morphology and dimension of conidia and production of chlamidospore the funguses identify as Fusarium solani. PMID:16637194

A series of metal(II) complexes of VO(II), Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized from the azo Schiff base ligand 4-((E)-4-((E)-(4-chlorophenyl)diazenyl)-2-hydroxybenzylideneamino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (CDHBAP) and characterized by elemental analysis, spectral (IR, UV-Vis, (1)H NMR, ESR and EI-mass), magnetic moment measurements, molar conductance, DNA, SEM, X-ray crystallography and fluorescence studies. The electronic absorption spectra and magnetic susceptibility measurements of the complexes indicate square pyramidal geometry for VO(II) and octahedral geometry for all the other complexes. The important infrared (IR) spectral bands corresponding to the active groups in the ligand and the solid complexes under investigation were studied and implies that CDHBAP is coordinated to the metal ions in a neutral tridentate manner. The redox behavior of copper(II) and vanadyl(II) complexes have been studied by cyclic voltammetry. The nuclease activity of the above metal(II) complexes shows that the complexes cleave DNA. All the synthesized complexes can serve as potential photoactive materials as indicated from their characteristic fluorescence properties. The antibacterial and antifungal activities of the synthesized ligand and its metal complexes were screened against bacterial species (Staphylococcus aureus, Salmonella typhi, Escherichia coli, Bacillus subtilis, Shigella sonnie) and fungi (Candida albicans, Aspergillus niger, Rhizoctonia bataicola). Amikacin and Ketoconozole were used as references for antibacterial and antifungal studies. The activity data show that the metal complexes have a promising biological activity comparable with the parent Schiff base ligand against bacterial and fungal species. The second harmonic generation (SHG) efficiency of the ligand was measured and the NLO (non-linear optical) properties of the ligand are expected to result in the realization of advanced optical devices in optical fiber communication (OFC) and optical computing. The SEM image of the copper(II) complex implies that the size of the particles is 1 ?m. PMID:22728967

Pseudomonas fluorescens NBRI2650 was isolated after screening 360 bacterial strains from the rhizosphere of chickpea (Cicer arietinum L.) grown in fungal-disease-suppressive field soil. The strain was selected because of its high rhizosphere competence and ability to inhibit the growth of Fusarium oxysporum f.sp. ciceri, Rhizoctonia bataticola, and Pythium sp. under in vitro conditions. Survival and colonization of NBRI2650 in the phytosphere of chickpea, cotton (Gossypium hirsutum L.), cucumber (Cucumis sativus L.), and tomato (Lycopersicon seculentum Mill.) were monitored using a chromosomally located rifampicin-marked mutant P. fluorescens NBRI2650R. The strain showed variable ability to invade and survive in the phytosphere of different plants. Chickpea was used as a tester plant for further work, as it was not invaded by NBRI2650R. The interaction between NBRI2650R and F oxysporum fsp. ciceri was studied by both light microscopy and scanning electron microscopy. The lysis of the fungal cell wall by NBRI2650R was clearly demonstrated. Treatment of the chickpea seeds with NBRI2650R in prerelease experiments in the greenhouse using disease-conducive field soils from Jhansi and Kanpur resulted in increased plant growth and did not result in any perturbation of the indigenous microbial community that inhabited the rhizosphere of chickpea compared with nonbacterized seeds. Direct fermentation of diluted NBRI2650R on vermiculite without the need of expensive fermentors offers a reliable process for manufacturing bacterial inoculants in developing countries. Under field conditions, the horizontal and vertical movement of NBRI2650R was restricted to 30 and 60 cm, respectively, and the strain could not survive in the field during the 7 months before the chickpea could be planted for next cropping season. Field trials conducted at Jhansi, Kanpur, and Pantnagar resulted in higher grain yield increase in the bacteria-treated seed compared with the nonbacterized control. Seed and furrow treatment of the two chickpeas ('Radhey' and 'H-208') at Pantnagar resulted in significantly (P = 0.05) greater seedling mortality in nonbacterized seedlings compared with bacterized ones. The seed dry weight and yield for each variety were also significantly higher in bacterized seedlings than in nonbacterized ones. The population of NBRI2650R persisted throughout the growing season of chickpea in the range of 5.4-6.4 log10 CFU/g root. PMID:12224558

The effects of persistent organic pollutants (POPs) on humans and biodiversity are multiple and varied. Nowadays environmentally-friendly pesticides are strongly preferred to POPs. It is noteworthy that the crop protection role of pesticides and other techniques, i.e. biopesticides, plant extracts, prevention methods, organic methods, evaluation of plant resistance to certain pests under an integrated pest management (IPM), could improve the risks and benefits which must be assessed on a sound scientific basis. For this directive it is crucial to bring about a significant reduction in the use of chemical pesticides, not least through the promotion of sustainable alternative solutions such as organic farming and IPM. Biopesticides are derived from natural materials such as animals, plants, bacteria, and certain minerals. Most of them are biodegradable in relatively short periods of time. On this regard, substances from Calceolaria species emerge as a strong alternative to the use of POPs. The American genus Calceolaria species are regarded both as a notorious weeds and popular ornamental garden plants. Some have medicinal applications. Other taxa of Calceolaria are toxic to insects and resistant to microbial attack. These properties are probably associated with the presence of terpenes, iridoids, flavonoids, naphthoquinones and phenylpropanoids previously demonstrated to have interesting biological activities. In this article a comprehensive evaluation of the potential utilization of Calceolaria species as a source of biopesticides is made. The chemical profile of selected members of the Chilean Calceolaria integrifolia sensu lato complex represents a significant addition to previous studies. New secondary metabolites were isolated, identified and tested for their antifeedant, insect growth regulation and insecticidal activities against Spodoptera frugiperda and Drosophila melanogaster. These species serve as a model of insect pests using conventional procedures. Additionally, bactericidal and fungicidal activity were determined. Dunnione mixed with gallic acid was the most active fungistatic and fungicidal combination encountered. Several compounds as isorhamnetin, combined with ferulic and gallic acid quickly reduced cell viability, but cell viability was recovered quickly and did not differ from that of the control. The effect of these mixtures on cultures of Aspergillus niger, Fusarium moniliforme, Fusarium sporotrichum, Rhizoctonia solani, and Trichophyton mentagrophytes, was sublethal. However, when fungistatic isorhamnetin and dunnione were combined with sublethal amounts of both ferulic and gallic acid, respectively, strong fungicidal activity against theses strains was observed. Thus, dunnione combined with gallic acid completely restricted the recovery of cell viability. This apparent synergistic effect was probably due to the blockade of the recovery process from induced-stress. The same series of phenolics (iridoids, flavonoids, naphthoquinones and phenylpropanoids) were also tested against the Gram-negative bacteria Escherichia coli, Enterobacter agglomerans, and Salmonella typhi, and against the Gram-positive bacteria Bacillus subtilis, Sarcinia lutea, and Staphylococcus aureus and their effects compared with those that of kanamycin. Mixtures of isorhamnetin/dunnione/kaempferol/ferulic/gallic acid in various combinations were found to have the most potent bactericidal and fungicidal activity with MFC between 10 and 50 ?g/ml. Quercetin was found to be the most potent fungistatic single compound with an MIC of 15 µg/ml. A time-kill curve study showed that quercetin was fungicidal against fungi assayed at any growth stage. This antifungal activity was slightly enhanced by combination with gallic acid. The primary antifungal action of the mixtures assayed likely comes from their ability to act as nonionic surfactants that disrupt the function of native membrane-associated proteins. Hence, the antifungal activity of isorhamnetin and other O-methyl flavonols appears to be mediated by biophysical processes. Maxim